ACYCLIC STEREOCHEMICAL CONTROL USING HEXACARBONYLDICOBALT STABILIZED PROPARGYL CATIONS. A HIGHLY STEREOSELECTIVE ROUTE TO 1β-METHYLCARBAPENEM PRECURSORS.

Article abstract of DOI:10.1016/S0040-4039(00)95993-8

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-<(1R)-1-t-butyldimethylsilyloxyethyl>-4-<(1R)-1-methyl-3-methoxycarbonyl-2-oxopropyl>-2-azetidin-2-one or hydrogenated and oxidatively cleaved to (3S,4S)-3-<(1R)-1-t-butyldimethylsilyloxyethyl>-4-<(1R)-1-carboxyethyl>-azetidin-2-one.