- 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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- ACYCLIC STEREOCHEMICAL CONTROL USING HEXACARBONYLDICOBALT STABILIZED PROPARGYL CATIONS. A HIGHLY STEREOSELECTIVE ROUTE TO 1β-METHYLCARBAPENEM PRECURSORS.
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A highly stereoselective route to precursors of 1β-methylcarbapenems is described.Hydride reduction of a hexacarbonyldicobalt stabilized propargyl cation derived from a 4-acyl-2-azetidinone prepared using the Weinreb ketone synthesis proceeds with complete stereochemical control to a 1β-methylcarbapenem precursor bearing an alkynyl unit.The alkyne is readily elaborated to (3S,4R)-3--4--2-azetidin-2-one or hydrogenated and oxidatively cleaved to (3S,4S)-3--4--azetidin-2-one.
- Prasad, J. Siva,Liebeskind, Lanny S.
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p. 1857 - 1860
(2007/10/02)
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