- Enantioselective lipase-catalyzed acetylation of β-lactam precursors of carbapenem antibiotics
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The Amano PS-lipase-catalyzed enantioselective acetylation in vinyl acetate of (±)-3-hydroxyethyl-β-lactams 3-6, useful precursors of carbapenem antibiotics, proceeds with high enantioselectivity (E > 98) to afford the corresponding acetates 3b-6b in optically pure form. The rate of acetylation is influenced by the relative stereochemistry of the C(3)-C(4) β-lactam carbon atoms, the trans isomers being transformed much faster than the cis ones. The stereochemical preference of the lipase-PS is for the (1′R,3R) enantiomers, as determined by chemical correlation. On the other hand, the lipase-PS-catalyzed hydrolysis of esters 3b,d in phosphate buffer proceeds with low selectivity and at a lower rate.
- Bucciarelli, Maria,Davoli, Paolo,Forni, Arrigo,Moretti, Irene,Prati, Fabio
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p. 2489 - 2494
(2007/10/03)
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- Preparation of Aminosaccharides Using Ester-Imine Condensations: Syntheses of Methyl N-Benzoylacosaminide and Methyl N-(Oxo(phenylmethoxy)acetyl)daunosaminide from (S)-Ethyl 3-Hydroxybutyrate
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The dianion of (S)-ethyl β-hydroxybutyrate (1) was treated with N-trimethylsilyl imine 2 to afford β-lactam 4.The same dianion reacted with N-aryl imine 10 to give β-lactams 11, 12, and 13.A three-step sequence was used to convert 4 into the β-lactam-pyra
- Galluci, Judith C.,Ha, Deok-Chan,Hart, David J.
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p. 1283 - 1292
(2007/10/02)
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- Asymmetric Synthesis of (1'R,3R,4R)-4-Acetoxy-3(1'-((tert-butyldimethylsilyl)oxy)ethyl)-2-azetidinone and Other 3-(1'-Hydroxyethyl)-2-azetidinones from (S)-(+)-Ethyl 3-Hydroxybutanoate: Formal Total Synthesis of (+)-Thienamycin
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The synthesis of (1'R,3R,4R)-4-acetoxy-3-(1'-((tert-butyldimethylsilyl)oxy)ethyl)-2-azetidinone, an important precursor for synthesis of carbapenems and penems, is detailed.The methodology utilized relies on the addition, cyclization reaction between the dianion of (S)-(+)-ethyl 3-hydroxybutanoate and N-arylaldimines.The syntheses of other useful optically active 3-(hydroxyethyl)-2-azetidinones are presented.A study of factors influencing the stereochemistry in the addition, cyclization reaction for the formation of 3-(1'-hydroxyethyl)-2-azetidinones is detailed.
- Georg, Gunda I.,Kant, Joydeep,Gill, Harpal S.
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p. 1129 - 1135
(2007/10/02)
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- 3-(1'-hydroxyethyl)-2-azetidinones from 3-hydroxybutyrates and N-arylaldimines
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Dianion imine addition, cyclisation reaction between ethyl-3-hydroxybutyrate and the aldimines generates β-lactams with the hydroxyethyl side chain of thienamycin and related β-lactam antibiotics in place. The effects of the N-arylaldimine and the reactio
- Georg,Gill,Gerhardt
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p. 3903 - 3906
(2007/10/02)
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- AN ENANTIOSELECTIVE APPROACH TO CARBAPENEM ANTIBIOTICS: FORMAL SYNTHESIS OF (+)-THIENAMYCIN
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An enantioselective synthesis of intermediates in synthesis of thienamycin (15) and epithienamycin-C (16) is described.
- Hart, David J.,Ha, Deok-Chan
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p. 5493 - 5496
(2007/10/02)
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