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  • 1.
    Andersson, Fredrik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Highly stereoselective alkylation of (S)-proline-based chiral auxiliaries2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15, no 16, p. 2539-2545Article in journal (Refereed)
    Abstract [en]

    Alkylation of the enolates of the propanoylamides of two chiral auxiliaries (S)-(-)-2-(pyrrolidin-2-yl)propan-2-ol 1a and (S)-(-)-2-(2-methoxypropan-2-yl)pyrrolidine 1b, derived from (S)-proline, with benzyl bromide and n-butyl iodide has been studied. The auxiliaries 1a and 1b induced opposite selectivity that is (R)- and (S)-configuration, respectively, at the newly created stereogenic centre. The diastereoselectivities and conversion yields in these alkylations were moderate to excellent. When Cp2ZrCl2 was used as an enolate coordinating agent, benzylation of propanoylated 1b gave an excellent diastereomeric ratio of 99:1. The benzylated diastereomeric products from either propanoylated 1a or 1b were easily separated by liquid chromatography.

  • 2.
    Andersson, Fredrik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Synthesis of two (S)-indoline-based chiral auxiliaries and their use in diastereoselective alkylation reactions2006In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 17, no 13, p. 1952-1957Article in journal (Refereed)
    Abstract [en]

    Two chiral auxiliaries, 2-[(S)-indolin-2-yl]propan-2-ol 1a and (S)-2-(2-methoxypropan-2-yl)indoline 1b, were synthesised from enantiomerically pure (S)-indoline-2-carboxylic acid 3. High diastereoselectivities in alkylations of enolates of the propanoylamides derived from the two auxiliaries are presented. Surprisingly, both auxiliaries induced the same selectivity at the newly created stereogenic centre. The benzyl bromide and n-butyl iodide alkylation reactions showed diastereomeric ratios that were moderate (81:19) to very good (96:4) and with very good yields (86-98%). When LiCl was used as an enolate coordinating agent, in the benzylation of the enolate from propanoylated auxiliary 1a, a very high crude diastereomeric ratio was obtained (99.7:0.3).

  • 3.
    Berglund, Per
    et al.
    KTH, Superseded Departments, Biotechnology.
    Vallikivi, I.
    Fransson, Linda
    KTH, Superseded Departments, Biotechnology.
    Dannacher, H.
    Holmquist, Mats
    KTH, Superseded Departments, Biotechnology.
    Martinelle, Mats
    KTH, Superseded Departments, Biotechnology.
    Björkling, F.
    Parve, O.
    Hult, Karl
    KTH, Superseded Departments, Biotechnology.
    Switched enantiopreference of Humicola lipase for 2-phenoxyalkanoic acid ester homologs can be rationalized by different substrate binding modes1999In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 10, no 21, p. 4191-4202Article in journal (Refereed)
    Abstract [en]

    Humicola lanuginosa lipase was used for enantioselective hydrolyses of a series of homologous 2-phenoxyalkanoic acid ethyl esters. The enantioselectivity (E-value) of the enzyme changed from an (R)-enantiomer preference for the smallest substrate, 2-phenoxypropanoic acid ester, to an (S)-enantiomer preference for the homologous esters with longer acyl moieties. The E-values span the range from E=13 (R) to E=56 (S). A molecular modeling study identified two different substrate-binding modes for each enantiomer. We found that the enantiomers favored different modes. This discovery provided a model that offered a rational explanation for the observed switch in enantioselectivity. (C) 1999 Elsevier Science Ltd. All rights reserved.

  • 4. Cele, Zamani E. D.
    et al.
    Sosibo, Sphelele C.
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Kruger, Hendrik G.
    Maguire, Glenn E. M.
    Govender, Thavendran
    Catalytic asymmetric carbon-carbon bond forming reactions catalyzed by tetrahydroisoquinoline (TIQ) N,N '-dioxide ligands2013In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 24, no 4, p. 191-195Article in journal (Refereed)
    Abstract [en]

    The use of TIQ-N,N'-dioxide ligands in asymmetric C-C bond forming reactions is described. In the Michael addition of cyclohexane-1,3-dione and malonates to beta,gamma-unsaturated alpha-ketoesters, excellent yields (up to 93%) and moderate to good enantioselectivities (70-89% ee) were obtained. The catalytic hetero-ene reaction of 2-methoxypropene with phenylglyoxal gave the ene product in excellent yield (95%) with moderate enantioselectivity (77% ee). The catalyst system performed well at temperatures ranging from 0 to 30 degrees C and relatively low catalyst loading (0.2-5 mol %) with dichloromethane being the preferred solvent for all reactions.

  • 5. Chakka, Sai Kumar
    et al.
    Francis, Vivian
    Cele, Zamani E. D.
    Sosibo, Sphelele C.
    Arvidsson, Per I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Kruger, Hendrik G.
    Maguire, Glenn E. M.
    Govender, Thavendran
    Asymmetric conjugate addition of thioglycolate to a range of chalcones using tetrahydroisoquinoline (TIQ) N,N '-dioxide ligands2012In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 23, no 8, p. 616-622Article in journal (Refereed)
    Abstract [en]

    A series of novel TIQ based N,N'-oxide ligands were synthesised and screened for their catalytic activity in the enantioselective conjugate addition of thioglycolate to chalcones. Bulky groups on the side chain of the TIQ backbone provided the highest enantioselectivity of up to 88% with 10 mol % catalyst loading. It was also observed that these reactions proceeded optimally in the presence of dichloromethane as a solvent. Screening of various metals emphasized La(OTf)(3) as the ideal pre-catalyst for this particular reaction.

  • 6. Chakka, Sai Kumar
    et al.
    Peters, Byron K.
    Andersson, Pher G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Maguire, Glenn E. M.
    Kruger, Hendrik G.
    Govender, Thavendran
    Iridium-catalyzed asymmetric hydrogenation of olefins using TIQ phosphine-oxazoline ligands2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 18, p. 2295-2301Article in journal (Refereed)
    Abstract [en]

    A novel family of tetrahydroisoquinoline (TIQ) phosphine-oxazoline ligands and four corresponding iridium complexes have been developed and applied to the asymmetric hydrogenation of unfunctionalized olefins. The results showed that the best conversion rates were observed in up to 99% with an enantiomeric excess of 91%.

  • 7.
    Datta, Gopal K.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Nordeman, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Dackenberg, Jakob
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Nilsson, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry. ORGFARM.
    Hallberg, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Larhed, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Enantiopure 2-Aryl-2-Methyl Cyclopentanones by an Asymmetric Chelation-Controlled Heck Reaction Using Aryl Bromides: Increased Preparative Scope and Effect of Ring Size on Reactivity and Selectivity2008In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 19, no 9, p. 1120-1126Article in journal (Refereed)
    Abstract [en]

    Quaternary 2-aryl-2-methyl cyclopentanones were obtained in 85–94% ee via Pd(0)-catalyzed chelation-controlled asymmetric arylation of a cyclopentenyl ether with aryl bromides and subsequent hydrolysis. Two new cyclohexenyl ethers were synthesized and evaluated as Heck substrates with both aryl iodides and bromides under different reaction conditions. Arylations of the six-membered vinyl ether 1-methyl-2-(S)-(cyclohex-1-enyloxymethyl)-pyrrolidine with aryl bromides were achieved with t-Bu3P-promoted palladium catalysis using either classical or microwave heating. Isolated Heck products were also obtained in high diastereoselectivities (94–98% de).

  • 8.
    Dinér, Peter
    Uppsala University.
    Catalytic asymmetric chiral lithium amide-promoted epoxide rearrangement: a NMR spectroscopic and kinetic investigation2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 21-22, p. 2733-2739Article in journal (Refereed)
  • 9.
    Dinér, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Catalytic asymmetric chiral lithium amide-promoted epoxide rearrangement: a NMR spectroscopic and kinetic investigation2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 21-22, p. 2733-2739Article in journal (Refereed)
    Abstract [en]

    The lithium amide derived from the chiral diamine (1R,3S,4S)-3-(1-pyrrolidinyl)methyl-2-azabicyclo[2.2.1]heptane, has been reported to catalytically deprotonate cyclohexene oxide and other epoxides, yielding chiral allylic alcohols in excellent enantiomeric excess. In this work, 6Li, 1H and 13 C NMR spectroscopy have been used to study the aggregation of the chiral lithium amide in THF and the influence on the aggregation by the addition of additives, such as 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU). The activated complex under catalytic deprotonation of cyclohexene oxide, that is, with excess Li-DBU and free DBU, is built from one monomer of the chiral lithium amide, one molecule of epoxide and one additional molecule of DBU. The reaction order (0.97) obtained for the bulk base Li-DBU shows an inverse dependence on the concentration, suggesting a deaggregation of the initial mixed dimer to a monomer-based transition state containing a monomer of the lithium amide.

  • 10.
    Dinér, Peter
    et al.
    University of Gothenburg.
    Pettersen, Daniel
    Nilsson Lill, Sten O.
    Ahlberg, Per
    Investigation of site selectivity of the stereoselective deprotonation of cyclohexene oxide using kinetic resolution of isotopic enantiomers in natural abundance2005In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 162665-2671, no 15, p. 2665-2671Article in journal (Refereed)
  • 11.
    Dziedzic, Pawel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Acyclic beta-amino acid catalyzed asymmetric anti-selective Mannich-type reactions2007In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 18, no 9, p. 1033-1037Article in journal (Refereed)
    Abstract [en]

     The ability of a primary amine containing acyclic beta(3)-amino acids to catalyze direct asymmetric anti-selective Mannich-type reactions is presented. The reactions are generally highly diastereo- and enantioselective to give the corresponding Mannich products with up to >19:1 dr (anti/syn) and 88-99% ee.

  • 12.
    Eriksson, Carina
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sjödin, Kristina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schlyter, Fredrik
    Swedish University of Agricultural Sciences, Alnarp.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Synthesis of (+)- and (-)-dihydropinidine by diastereoselective dimethylzinc promoted allylation of 2-methyltetrahydropyridine-N-oxide with allylboronic ester.2006In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 17, no 7, p. 1074-1080Article in journal (Refereed)
    Abstract [en]

    The enantiomers of the naturally occurring alkaloid dihydropinidine 1, potential antifeedants against the pine weevil, Hylobius abietis, were prepared by diastereoselective, dimethylzinc mediated addition of pinacolyl 2-propenylboronate 14 to nitrones (R)- and (S)-2-methyl tetrahydropyridine-N-oxide 3, prepared from d- and l-alanine, respectively.

  • 13. Eriksson, Carina
    et al.
    Sjödin, Kristina
    Schlyter, Fredrik
    Högberg, Hans-Erik
    Synthesis of (+)- and (−)-dihydropinidine by diastereoselective dimethylzinc promoted allylation of 2-methyltetrahydropyridine-N-oxide with an allylboronic ester2006In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 17, no 7, p. 1074-1080Article in journal (Refereed)
    Abstract [en]

    The enantiomers of the naturally occurring alkaloid dihydropinidine 1, potential antifeedants against the pine weevil, Hylobius abietis, were prepared by diastereoselective, dimethylzinc mediated addition of pinacolyl 2-propenylboronate 14 to nitrones (R)- and (S)2-methyl tetrahydropyridine-N-oxide 3, prepared from D- and L-alanine, respectively.

  • 14. Hallman, K.
    et al.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Polymer-bound bis(oxazoline) as a chiral catalyst2001In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 12, no 10, p. 1475-1478Article in journal (Refereed)
    Abstract [en]

    A chiral bis(oxazoline) was grafted on ArgoGel and used in the palladium-catalysed substitution of (+/-)-1,3-diphenyl-2-propenyl acetate with dimethyl malonate. The enantioselectivity was the same as that observed when the analogous monomeric catalyst was used (94-95% e.e.), despite the fact that the C-2 symmetry of the ligand was affected when coupled to the polymer. The polymer-supported catalyst could be recycled several times after removal of precipitated Pd(0). The polymer-bound bis(oxazoline) was also applied in a zinc-catalysed Diels-Alder reaction but lower selectivity and reactivity than the monomer was observed.

  • 15.
    Hammar, Peter
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Córdova, Armando
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University.
    Himo, Fahmi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Density Functional Theory Study of the Stereoselectivity in Small Peptide-Catalyzed Intermolecular Aldol Reactions2008In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 19, p. 1617-1621Article in journal (Refereed)
    Abstract [en]

    The origins of the stereoselection of the dipeptide-catalyzed intermolecular aldol reaction are explored by means of hybrid density functional theory. Transition states were located for the (S)-ala-(S)-ala-catalyzed aldol reaction with cyclohexanone as the donor and benzaldehyde as the acceptor. The calculations reproduce the experimental trends very satisfactorily. It is demonstrated that the main Source of stereoselectivity is the interaction of the N-terminal amino acid side chain of the dipeptide with the cyclohexene ring.

  • 16.
    Hartikka, Antti
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Hojabri, Leila
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Bose, Pratim
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Arvidsson, Per I.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Synthesis and application of novel imidazole and 1H-tetrazolic acid containing catalysts in enantioselective organocatalyzed Diels-Alder reactions2009In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 20, no 16, p. 1871-1876Article in journal (Refereed)
    Abstract [en]

    Herein we report studies on the organocatalytic Diels-Alder reaction using a variety of catalysts capable of activating alpha,beta-unsaturated carbonyl compounds for reactions with dienes. The structurally attractive catalysts 4 and 14 were utilized in the enantioselective organocatalytic Diels-Alder reactions. Catalyst 4 provided the products in fair yields and more importantly in good enantioselectivities of up to 83% ee. Catalyst 14 was synthesized in high yield and was assessed in the enantioselective organocatalytic Diels-Alder reaction. Catalyst 14 proved to be a highly active and selective catalyst providing the products in high yield and high enantioselectivities up to 95% ee. (C) 2009 Elsevier Ltd. All rights reserved.

  • 17.
    Hartikka, Antti
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Slosarczyk, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Arvidsson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Application of novel sulfonamides in enantioselective organocatalyzed cyclopropanation2007In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 18, no 12, p. 1403-1409Article in journal (Refereed)
    Abstract [en]

    Three novel aryl sulfonamides derived from (2S)-indoline-2-carboxylic acid have been obtained and used as organocatalysts. The catalysts incorporate diverse functionality on the phenyl ring, enabling steric, and electronic fine tuning of the catalysts. The catalysts facilitate the reaction between a range of α,β-unsaturated aldehydes and sulfur ylides, thus providing cyclopropane products in enantiomeric excesses of up to 99%.

  • 18.
    Hedenström, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nguyen, Ba-Vu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Silks III, L. A.
    Do enzymes recognise remotely located stereocentres?: Highly enantioselective Candida rugosa lipase-catalysed esterification of the 2- to 8-methyldecanoic acids2002In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 13, no 8, p. 835-844Article in journal (Refereed)
    Abstract [en]

    Several racemic methyl decanoic acids have been synthesised and successfully resolved in esterification with 1-hexadecanol at aw=0.8 in cyclohexane using immobilised Candida rugosa lipase (CRL) as the catalyst. The enantiomeric ratios (E=2.8-68) obtained were surprisingly high even when the methyl group was as remotely located as in 8-methyldecanoic acid (E=25). Interestingly, the lipase shows enantiopreference for the S-enantiomer when the methyl group is located on even numbered carbons i.e. for the 2-,4-,6- and 8-methyldecanoic acids and to the R-enantiomer when the methyl group is located on uneven numbered carbons i.e. for the 3-,5- and 7-methyldecanoic acids.

  • 19.
    Holmberg, Pär
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry.
    Karlsson, John
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Enzymatic Kinetic Resolution of 1-(3-furyl)-3-buten-1ol2005In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 16, p. 2397-2399Article in journal (Other academic)
    Abstract [en]

    The enzymatic kinetic resolution of 1-(3-furyl)-3-buten-1-ol was investigated via the enantioselective hydrolysis of the corresponding acetate. Pseudomonas fluorescens (Fluka) was found to give the highest enantiomeric ratios of the 11 lipases screened. At 51% conversion, the ee value (eep) for the product was found to be 89%, giving an enantiomeric ratio (Ep) of 58, while the ee value (ees) for the substrate was 89%, giving an enantiomeric ratio (Ep) of 38.

  • 20. Högberg, Hans-Erik
    et al.
    Edlund, Helen
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Hedenström, Erik
    WATER ACTIVITY INFLUENCES ENANTIOSELECTIVITY IN A LIPASE-CATALYZED RESOLUTION BY ESTERIFICATION IN AN ORGANIC-SOLVENT1993In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 4, no 10, p. 2123-2126Article in journal (Refereed)
    Abstract [en]

    The enantioselectivity of Candida rugosa lipase-mediated esterification of 2-methylalkanoic acids with n-alcohols in cyclohexane is dependent on water activity.

  • 21.
    Isaksson, Dan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sjödin, Kristina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Enantiomerically enriched cryptone by lipase catalysed kinetic resolution2006In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 17, no 2, p. 275-280Article in journal (Refereed)
    Abstract [en]

    Thiophenol was added to racemic cryptone (4-isopropyl-2-cyclohexene-1-one) and the resulting 1,4-addition products, cis- and trans-4-isopropyl-3-(phenylsulfanyl)cyclohexanone) were separated and the latter reduced to rac-1,3-cis-1,4-trans-4-isopropyl-3-(phenylsulfanyl)cyclo¬he¬xanol which was subjected to lipase catalysed resolution by acylation catalysed by CAL-B (Candida antarctica lipase B). The remaining alcohol was separated from the produced acetate, which was hydrolysed to the alcohol. The enantiomeric alcohols so obtained were oxidised. The initial products, probably sulfoxidoketones spontaneously decomposed to furnish enantiomerically enriched (R)- and (S)-cryptone with up to 76% and 98% ee, respectively.

  • 22. Isaksson, Dan
    et al.
    Sjödin, Kristina
    Högberg, Hans-Erik
    Enantiomerically enriched cryptone by lipase catalysed kinetic resolution2006In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 17, no 2, p. 275-280Article in journal (Refereed)
    Abstract [en]

    Thiophenol was added to racemic cryptone (4-isopropyl-2-cyclohexene-1-one) and the resulting 1,4-addition products, cis- and trans-4-isopropyl-3- (phenylsulfanyl)cyclohexanone were separated and the latter reduced to rac-1,3-cis-1,4-trans-4-isopropyl-3-(phenylsulfanyl)cyclohexanol, which was subjected to lipase catalysed resolution by acylation catalysed by CAL-B (Candida antarctica lipase B). The alcohol enantiomers obtained were oxidised. The remaining alcohol was separated from the produced acetate, which was hydrolysed to the alcohol. The initial products, probably sulfoxidoketones spontaneously decomposed to furnish enantiomerically enriched (R)- and (S)-cryptone with up to 76% and 98% ee, respectively

  • 23. Kawthekar, Rahul B.
    et al.
    Chakka, Sai Kumar
    Francis, Vivian
    Andersson, Pher G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Kruger, Hendrik G.
    Maguire, Glenn E. M.
    Govender, Thavendran
    Synthesis of tetrahydroisoquinoline (TIQ)-oxazoline ligands and their application in enantioselective Henry reactions2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 7, p. 846-852Article in journal (Refereed)
    Abstract [en]

    A novel family of eleven new tetrahydroisoquinoline (TIQ)-oxazoline intermediates and five corresponding copper(II) catalysts has been developed and applied to the catalytic asymmetric Henry reaction of various aldehydes with nitromethane to provide beta-hydroxy nitroalkanes in high conversion (>99%) This paper describes the synthesis of the TIQ compounds from L-dihydroxyphenylalanine (L-DOPA) as the starting material The chiral ligands were complexed in situ with various transition metals such as Cu, Sc, Co, Zn, Ni and Mn and tested as a chiral catalyst for the Henry reaction The reaction was optimized in terms of the metal, counter ion, solvent, temperature and over a range of substrates The corresponding catalyst with copper(II) acetate and 2-propanol as the solvent provides the best enantioselectivities (up to 77% ee) of the corresponding nitroalcohol for 4-chlorobenzaldehyde.

  • 24. Lake, F.
    et al.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Ti-mediated addition of diethylzinc to benzaldehyde. The effect of chiral additives2001In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 12, no 5, p. 755-760Article in journal (Refereed)
    Abstract [en]

    In the presence of a chiral tridentate bissulfonamide, the titanium-mediated addition of diethylzinc to benzaldehyde gave alkylated products ranging from the (R)-enantiomer, formed with an e.e. of 26%, to the (S)-enantiomer, formed in 72% e.e. The enantioselectivity was also affected by the presence of additional chiral mono- and bidentate ligands, with the reactions proceeding via complexes containing the chiral sulfonamide and the additive. The: addition of (1R,2R)-2,2-diphenyl-,12-ethanediamine and (1S,2S)-1.3-diphenyl-1,2-ethanediamine gave the (S)-product with e.e. of 49% and the (R)-product with 16% e.e., respectively, whereas without additives the (R)-product was obtained in 26% e.e, In the presence of (1R,2R)-1,2-diphenyl-1,2-ethanediamine only (i.e. without the chiral sulfonamide), the (S)-product formed with a 3% e.e.

  • 25.
    Larsson, Michael
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Jimmy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Liu, Rong
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Enantiopure building blocks for the synthesis of 3-methyl-2-alkanols: Diastereoselective methylmetal addition to a chiral 2-methylaldehyde followed by lipase catalysed esterification2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15, no 18, p. 2907-2915Article in journal (Refereed)
    Abstract [en]

    The racemic synthetic building block (2R*,3R*)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2R*,3R*)-2 was obtained in a high diastereomeric ratio [95:5, (2R*,3R*)/(2R*,3S*)-ratio] by Lewis acid catalysed dimethylzinc addition to racemic 2-methyl-3-(phenylsulfanyl)propanal (rac-1). Two consecutive acylations with vinyl acetate catalysed by Chirazyme L-2 (immobilised Candida antarctica lipase 13, CAL-B) led to preferential esterification of three of the four stereoisomers leaving (2S,3S)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2S,3S)-2 of 98:2 dr and 98% ee. The stereoisomerically impure acetate of (2R,3R)-3-methyl-4-(phenyisulfanyl)butan-2-ol (2R,3R)-2, obtained in the first CAL-B-catalysed acylation step, was hydrolysed and reesterified using CAL-A (immobilised Novozyme SP 525) as the catalyst, which left (2R,3R)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2R,3R)-2 of 98:2 dr and 99% ee as the remaining substrate. The individual enantiomers of 2-methyl-3-(phenylsulfanyl)propanal 1 were prepared from readily available (S)- and (R)-3-hydroxy-2-methylpropanoic acid methyl ester and reacted with dimethylzinc to give both enantiomers of (2R*,3R*)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2R, 3R)- or (2S,3S)-2 of both high dr and ee. These products were purified by lipase catalysed acylation to give the enantiomerically and diastereomerically highly pure enantiomers (>99.5:0.5 dr, >99.9% ee). Pure (2S,3S)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2S,3S)-2 was transformed into a potential pheromone precursor isolated from some pine sawflies of the genus Gilpinia, (2S,3R)-3-methylpentadecan-2-ol in 54% yield over eight steps.

  • 26.
    Larsson, Michael
    et al.
    Mittunivesitetet.
    Andersson, Jimmy
    Mittuniversitetet.
    Liu, Rong
    Mittuniversitetet.
    Högberg, Hans-Erik
    Mittuniversitetet.
    Enantiopure building blocks for the synthesis of 3-methyl-2-alkanols. Diastereoselective methylmetal addition to a chiral 2-methylaldehyde followed by lipase catalysed esterification2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15, p. 2907-2915Article in journal (Refereed)
    Abstract [en]

    The racemic synthetic building block (2R*,3R*)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2R*,3R*)-2 was obtained in a high diastereomeric ratio [95:5, (2R*,3R*)/(2R*,3S*)-ratio] by Lewis acid catalysed dimethylzinc addition to racemic 2-methyl-3-(phenylsulfanyl)propanal (rac-1). Two consecutive acylations with vinyl acetate catalysed by Chirazyme L-2 (immobilised Candida antarctica lipase 13, CAL-B) led to preferential esterification of three of the four stereoisomers leaving (2S,3S)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2S,3S)-2 of 98:2 dr and 98% ee. The stereoisomerically impure acetate of (2R,3R)-3-methyl-4-(phenyisulfanyl)butan-2-ol (2R,3R)-2, obtained in the first CAL-B-catalysed acylation step, was hydrolysed and reesterified using CAL-A (immobilised Novozyme SP 525) as the catalyst, which left (2R,3R)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2R,3R)-2 of 98:2 dr and 99% ee as the remaining substrate. The individual enantiomers of 2-methyl-3-(phenylsulfanyl)propanal 1 were prepared from readily available (S)- and (R)-3-hydroxy-2-methylpropanoic acid methyl ester and reacted with dimethylzinc to give both enantiomers of (2R*,3R*)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2R, 3R)- or (2S,3S)-2 of both high dr and ee. These products were purified by lipase catalysed acylation to give the enantiomerically and diastereomerically highly pure enantiomers (>99.5:0.5 dr, >99.9% ee). Pure (2S,3S)-3-methyl-4-(phenylsulfanyl)butan-2-ol (2S,3S)-2 was transformed into a potential pheromone precursor isolated from some pine sawflies of the genus Gilpinia, (2S,3R)-3-methylpentadecan-2-ol in 54% yield over eight steps.

  • 27.
    Li, Jia-Qi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Paptchikhine, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Govender, Thavendran
    Andersson, Pher G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Bicyclic phosphine-thiazole ligands for the asymmetric hydrogenation of olefins2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 11-12, p. 1328-1333Article in journal (Refereed)
    Abstract [en]

    New bicyclic thiazole-based chiral N,P-chelating ligands were developed. High activities and enantioselectivities were achieved in the iridium-catalyzed asymmetric hydrogenation of olefins with the new ligands.

  • 28.
    Liu, Rong
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Högberg, Hans-Erik
    Mittuniversitetet.
    Preparation of the four stereoisomers of 3-bromo-2-butanol or their acetates via lipase-catalysed resolutions of the racemates derived from dl- or meso-2,3-butanediol.2005In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 16, p. 2607-2611Article in journal (Refereed)
    Abstract [en]

    The four stereoisomeric 3-bromo-2-butanols and/or their acetates were prepared via lipase-catalysed kinetic resolution by hydrolyses of the acetates of the (+/-)-syn- and (+/-)-anti-3-bromo-2-butanols, or via esterifications of the alc hols. The diastereomeric bromoacetates were obtained by syntheses from the dl- and meso-2,3-butanediols, respectively. On a preparative scale, the four stereoisomers, either as the free alcohols or as their acetates, were obtained in > 95% ee, and in 35-40% yield (based on the starting racemates).

  • 29.
    Liu, Rong
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Berglund, Per
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Preparation of the four stereoisomers of 3-bromo-2-butanol or their acetates via lipase-catalysed resolutions of the racemates derived from dl- or meso-2,3-butanediol2005In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 16, no 15, p. 2607-2611Article in journal (Refereed)
    Abstract [en]

    The four stereoisomeric 3-bromo-2-butanols and/or their acetates were prepared via lipase-catalysed kinetic resolution by hydrolyses of the acetates of the (+/-)-syn- and (+/-)-anti-3-bromo-2-butanols, or via esterifications of the alc hols. The diastereomeric bromoacetates were obtained by syntheses from the dl- and meso-2,3-butanediols, respectively. On a preparative scale, the four stereoisomers, either as the free alcohols or as their acetates, were obtained in > 95% ee, and in 35-40% yield (based on the starting racemates).

  • 30.
    Liu, Rong
    et al.
    Mittuniversitetet.
    Högberg, Hans-Erik
    Mittuniversitetet.
    Chemoenzymatic preparation of (2S,3S)- and (2R,3R)-2,3-butanediols and their esters from mixtures of d,l- and meso-diols2001In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 12, no 5, p. 771-778Article in journal (Refereed)
    Abstract [en]

    An efficient method of preparing the pure enantiomers of 2,3-butanediol front commercially available mixtures of the d,l- and meso-isomers was developed. It furnished (2S,3S)-2.3-butanediol with > 99% e.e. and a >9.5/0.5 diastereomeric ratio and (2R,3R)-2,3-butanediol in 95% e.e. and >9.5/<5 diastereomeric ratio.

  • 31. Lutsenko, S.
    et al.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Microwave-mediated ruthenium-catalyzed asymmetric hydrogen transfer2001In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 12, no 18, p. 2529-2532Article in journal (Refereed)
    Abstract [en]

    Ru-catalyzed hydrogen transfer from propan-2-ol to acetophenone under microwave conditions using monotosylated (R,R)-diphenylethylenediamine as the chiral source afforded (R)-1-phenylethanol in >90% yield and 82% e.e. within 9 min, while use of ephedrine or norephedrine gave the same compound in high yield with 70 and 46% e.e., respectively. t-Butylphenylketone was reduced to (R)-2,2-dimethyl-1-phenyl-1-propanoI under the same conditions in close to quantitative yield, although with low enantioselectivity.

  • 32. Manner, Sophie
    et al.
    Hansson, Cecilia
    Larsson, Johanna M.
    Oltner, Viveca T.
    Frejd, Torbjoern.
    Asymmetric baker's yeast reductions of bridgehead-substituted bicyclo[2.2.2]octane-2,6-dione derivatives followed by conversion into catalytically active BODOLs for the diethylzinc addition to benzaldehyde.2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 11-12, p. 1374-1381Article in journal (Refereed)
    Abstract [en]

    4-Substituted bicyclo[2.2.2]octane-2,6-diones I [R = acetyl, benzyl, allyl, etc.] have been synthesized and tested as substrates in the enantioselective redn. with baker's yeast to give the corresponding hydroxy ketones II [R = acetyl, benzyl, allyl, etc.]. It was found that the deriv. bearing a TIPSO group at the 4-position was not reduced at all while that with a TBDMSO group gave 87% yield and 46% ee. Other 4-oxy functionalized derivs. were reduced with varying yields (36-87%) and ees (10-82%). The best result was obtained for the 4-Oallyl deriv. (80% yield, 82% ee). The hydroxy ketones carrying the benzyloxy and allyloxy groups at the 4-position were converted into the corresponding BODOLs III [R = allyl, benzyl], which were tested as catalysts in the diethylzinc addn. to benzaldehyde. In this reaction the ees were 90% and 89%, resp., which showed that BODOLs substituted at the 4-position are essentially as good catalysts in this reaction as those bearing a hydrogen. [on SciFinder(R)]

  • 33. Naicker, Tricia
    et al.
    Petzold, Katja
    Singh, Thishana
    Arvidsson, Per I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Kruger, Hendrik G.
    Maguire, Glenn E.M.
    Govender, Thavendran
    Novel tetrahydroisoquinoline based organocatalysts for asymmetric Diels–Alder reactions: insight into the catalytic mode using ROESY NMR and DFT studies2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 23, p. 2859-2867Article in journal (Refereed)
    Abstract [en]

    For the first time an organocatalyst bearing a secondary nitrogen within a cyclohexane ring has been evaluated in the asymmetric Diels–Alder reaction. This organocatalyst is also the first of its kind based on a (1R,3S)-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline backbone. These catalysts were tested over a range of dienes and dienophiles and displayed promising chemical conversions of up to 100% with up to 64% ee with triflic acid as the cocatalyst. Density functional theory computational studies and 2D NMR spectroscopy were used to determine the structure of the intermediate iminium ion formed between the most efficient catalyst and cinnamaldehyde. The reaction profile for each of the four possibilities in this reaction were calculated and it was found that the iminium intermediate leading to the major product is higher in energy but kinetically preferred. The activation energies of all possible reaction paths were calculated and the results correlated with the observed products. These experiments revealed that the presence of both (E)- and (Z)-isomers of the cinnamaldehyde were contributing factors for the low enantioselectivity of the reaction products.

  • 34.
    Olsson, Johan D M
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oscarson, Stefan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of phosphorylated Neisseria meningitidis inner core lipopolysaccharide structures2009In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 20, no 6/8, p. 879-886Article in journal (Refereed)
  • 35. Peters, Byron K.
    et al.
    Chakka, Sai Kumar
    Naicker, Tricia
    Maguire, Glenn E. M.
    Kruger, Hendrik G.
    Andersson, Pher G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Govender, Thavendran
    Synthesis of tetrahydroisoquinoline-diamine ligands and their application in asymmetric transfer hydrogenation2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 6, p. 679-687Article in journal (Refereed)
    Abstract [en]

    The use of the tetrahydroisoquinoline scaffold is well documented in biologically active compounds. However, reports of the utilisation of tetrahydroisoquinoline compounds in asymmetric catalysis are limited. The synthesis of novel diamine ligands possessing the tetrahydroisoquinoline (tetrahydroisoquinoline) backbone and evaluation of their activity in the asymmetric transfer hydrogenation of acetophenone are presented. The diamine ligands in conjunction with i-PrOH as the hydrogen source and [RhCl2(Cp*)](2) as the metal precursor proved to be the most effective of the tetrahydroisoquinoline derivatives for this catalytic system. Water was found to have a profound influence on the enantioselectivity of the reaction. Optimisation of the amount water, i-PrOH and catalytic loading content rendered the best result of 70% enantioselectivity for the (S)-1-phenylethanol isomer product.

  • 36. Pettersen, D.
    et al.
    Dinér, Peter
    University of Gothenburg.
    Amedjkouh, M.
    Ahlberg, P.
    Composition and structure of activated complexes in stereoselective deprotonation of cyclohexene oxide by a mixed dimer of chiral lithium amide and lithiated imidazole2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15, no 10, p. 1607-1613Article in journal (Refereed)
  • 37.
    Ramstadius, Clinton
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Boklund, Mikael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conversion of fructose into a building block for the synthesis of carbocyclic mannose mimics2011In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 22, no 4, p. 399-405Article in journal (Refereed)
    Abstract [en]

    Fructose was converted into C-1 diastereomeric carbocyclic building blocks resembling mannose using ruthenium-catalysed ring-closing metathesis as a key step. The potential use of the compounds in the synthesis of valienamine pseudodisaccharides is demonstrated using Mitsunobu coupling chemistry directly between a carbohydrate sulfonamide and the carbasugar C-1 alcohols.

  • 38.
    Ramstadius, Clinton
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hekmat, Omid
    Department of Biochemistry, Lund University.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Stålbrand, Henrik
    Department of Biochemistry, Lund University.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    β-Mannosidase and β-hexosaminidase inhibitors: synthesis of 1,2-bis-epi-valienamine and 1-epi-2-acetamido-2-deoxy-valienamine from D-mannose2009In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 20, no 6-8, p. 795-807Article in journal (Refereed)
    Abstract [en]

    A partially protected C-5C-5a unsaturated carbasugar with α-lyxo configuration is synthesised in five steps and 26% overall yield from a known mannose-derived hemiacetal, using ring-closing metathesis as a key step. This carbasugar is converted into valienamine derivatives with β-lyxo (i.e., corresponding to β-manno at C-1–C-4), α-lyxo (i.e., corresponding to α-manno at C-1–C-4) and β-2-acetamido-2-deoxy-xylo (i.e., corresponding to β-GlcNAc at C-1–C-4) configurations. This is the first report of the synthesis of the β-lyxo compound, 1,2-bis-epi-valienamine, which was found to inhibit Cellulomonas fimi β-mannosidase (CfMan2A) with Ki 140 μM. We report the crystal structures of three protected C-5C-5a unsaturated carbasugars with lyxo configuration.

  • 39. Risberg, E.
    et al.
    Somfai, Peter
    KTH, Superseded Departments, Chemistry.
    Enantioselective addition of organolithium reagents to a 2H-azirine2002In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 13, no 18, p. 1957-1959Article in journal (Refereed)
    Abstract [en]

    3-(2-Naphthyl)-2H-azirine was used as a model substrate in the first enantioselective addition of organolithium reagents to an azirine. Various organolithium reagents have been used together with different chiral ligands.

  • 40.
    Sabbani, Sunil
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Jimmy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Lipase catalyzed acylation of primary alcohols with remotely located stereogenic centres : the resolution of (± ) -4,4 -dimethyl -3 -phenyl -1 -pentanol2007In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 18, no 14, p. 1712-1720Article in journal (Refereed)
    Abstract [en]

    Enantioselective acylation of some (±)-3-alkyl-3-phenyl-l-propanols was performed with enzymes as catalysts. Moderate enantiomeric ratios (E), ranging up to E = 11.6, were obtained. In the resolution, some of the lipases selectively acylated the (+)-enantiomer while others acylated the (-)-enantiomer of the γ-substituted primary alcohols 1-4. Thus, it is possible to obtain both enantiomers of the alcohols as remaining substrate with high enantiomeric purity. The resolution of (±)-4,4-dimethyl-3-phenyl-1-pentanol 4 was extensively studied and screening experiments were conducted to select suitable lipase(s), reaction medium, acyl donor and appropriate temperature combinations to increase the enantiomeric ratio. Chirazyme® L-6/chloroform/vinyl propionate/38 °C and Chirazyme® L-7/di-iso-propyl ether/vinyl propionate/0 °C were chosen to obtain both enantiomers, (R)-(+)-4 and (S)-(-)-4, respectively, via sequential resolutions in excellent enantiomeric excess (>98%) and in 25% and 22% yield, respectively.

  • 41.
    Sawant, Rajiv T.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Stevenson, Joanne
    Odell, Luke R.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Arvidsson, Per I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Organocatalytic asymmetric cross-aldol reaction of 2-chloroethoxy acetaldehyde: diversity-oriented synthesis of chiral substituted 1,4-dioxanes and morpholines2013In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 24, no 2-3, p. 134-141Article in journal (Refereed)
    Abstract [en]

    Herein we report a facile organocatalytic asymmetric direct cross-aldol reaction of 2-chloroethoxy acetaldehyde with aromatic aldehydes using (S)-(-)-alpha,alpha-diphenyl-2-pyrrolidinemethanol as an organocatalyst to afford anti-2-(2-chloroethoxy)-1-arylpropane-1,3-diols with excellent enantioselectivities (95-98%) and moderate diastereoselectivities (3.5-7:1). The 1,3-diols, obtained after the aldehyde reduction, represent highly functional intermediates that allow for further diversification into both chiral 1,4-dioxanes and morpholines, compounds that frequently display interesting biological activities.

  • 42. Sobkowski, Michal
    et al.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kraszewski, Adam
    Stereochemistry of internucleotide bond formation by the H-phosphonate method. 7. Stereoselective formation of ribonucleoside (R-P)- and (S-P)-3 '-H-phosphonothioate monoesters2010In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 21, no 4, p. 410-419Article in journal (Refereed)
    Abstract [en]

    Ribonucleoside 3'-H-phosphonothioate monoesters exist in the form of (R-P)- and (S-P)-diastereomers. In order to obtain them in good yields and in high stereochemical purity, stereoselective strategies for their preparation were investigated. For the synthesis of the (R-P)-isomer, a stereoselective sulfhydrolysis of an activated nucleoside H-phosphonate was developed, while the monoesters with an (S-P)-configuration were prepared by asymmetric transformation of diastereomeric mixtures of nucleoside 3'-H-phosphonothioates using either a condensation with 9-fluorenemethanol, followed by beta-elimination, or via pivaloylation-hydrolysis reaction sequence. A tentative assignment of the absolute configurations of the obtained diastereomers of 3'-H-phosphonothioate esters was carried out via a stereochemical correlation analysis.

  • 43. Sott, R.
    et al.
    Granander, J.
    Dinér, Peter
    Göteborg University.
    Hilmersson, G.
    Solution structures of chiral lithium amides with internal sulfide coordination: sulfide versus ether coordination in chiral lithium amides2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15267-274, no 2, p. 267-274Article in journal (Refereed)
  • 44.
    Tilliet, Mélanie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Frölander, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Levacher, Vincent
    UMR 6014 IRCOF, CNRS, Université et INSA de Rouen.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Convenient Preparation of Bifunctional Pybox Ligands2008In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 64, no 44, p. 10244-10249Article in journal (Refereed)
    Abstract [en]

     Starting from a common easily available pybox derivative, chiral ditopic ligands with pendant Lewis basic sites consisting of amine or phosphine oxide functions attached in the 4-positions of the oxazoline rings were prepared by simple synthetic procedures. From the same pybox derivative, a macrocyclic ligand containing a diaza-18-crown-6-ether ring linked via triazole groups was obtained employing 'click' chemistry.

  • 45.
    Trifonova, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    The use of nonactivated iminodienophiles in the stereoselective aza-Diels-Alder reaction2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15, no 3, p. 445-452Article in journal (Refereed)
    Abstract [en]

    This paper describes the preparation of nitrogen-containing bicycles by the aza-Diels–Alderreaction ofnonactivatediminodienophiles and cyclopentadiene. Readily available starting materials such as (S)-(−)-lactate and l-amino acids were used for the preparation of chiral aldehydes with high enantiomeric excess. The improved oxidation procedure by Dess–Martin periodinane was employed for the synthesis of l-alanine derived phthalimide protected aldehyde 14, which was difficult to obtain in high enantiomeric excess by other methods. The influence of different Lewis acids on the stereoselectivity of the aza-Diels–Alderreactionwas also investigated: It was found that the use of a combination of BF3·Et2O and TFA in the cycloaddition leads to complete racemization of the imine prepared from 14 whereas the use of TiCl4 gives the cycloaddition products 17a and 17b with high enantioselectivity (90%).

  • 46.
    Vafiadi, Christina
    et al.
    National Technical University of Athens.
    Topakas, Evangelos
    National Technical University of Athens.
    Wong, Ken K.Y.
    Suckling, Ian D.
    Christakopoulos, Paul
    Mapping the hydroltic and synthetic selectivity of a type C feruloyl esterase (StFaeC) from Sporotrichum thermophile using alkyl ferulates2005In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 16, no 2, p. 373-379Article in journal (Refereed)
    Abstract [en]

    The active site of Sporotrichum thermophile type C feruloyl esterase (StFaeC) was probed using a series of C1–C4 alkyl ferulates. The affinities for straight and branched alkyl ferulates were demonstrated by the Km values of 1.64–0.51 and 0.19–0.1, respectively. Comparison of kcat and kcat/Km values shows that the enzyme hydrolyzed n-propyl ferulate faster and iso-propyl ferulate more efficiently. Alkyl ferulates were applied also for substrate selectivity mapping of feruloyl esterase to catalyze feruloyl group transfer to l-arabinose, using as a reaction system a ternary water–organic mixture consisting of n-hexane, t-butanol and water. Lengthening the aliphatic side chain was the most significant factor causing lower synthetic activity of the enzyme. The reaction parameters affecting the feruloylation rate and the conversion of the enzymatic process, such as the temperature and substrate concentration have been investigated. Under identical reaction conditions, the enzyme feruloylated other monosaccharides such as d-arabinose, d-glucose, d-xylose, d-mannose, d-fructose, d-galactose, d-ribose and model substrates such as 4-nitrophenyl α-l-arabinofuranoside and 4-nitrophenyl α-l-arabinopyranoside.

  • 47.
    Wang, Bo
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Liu, Y.
    Zhang, D.
    Feng, Y.
    Li, J.
    Efficient kinetic resolution of amino acids catalyzed by lipase AS 'Amano' via cleavage of an amide bond2012In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 23, no 18-19, p. 1338-1342Article in journal (Refereed)
    Abstract [en]

    Herein the efficient kinetic resolution of non-natural alpha-amino acids catalyzed by lipase AS 'Amano' via cleaving the amide bond is reported. The starting materials were the corresponding amino acid amides and the amino acids were generated with ees of up to 99% with E values of >600. These results indicated that the lipase AS 'Amano' could be a powerful amide hydrolase for the kinetic resolution of amino acid starting from the corresponding amino acid amides.

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