A highly stereoselective synthesis of a key intermediate of 1β-methylcarbapenems employing the reformatsky reaction of 3-(2-bromopropionyl)-2-oxazolidone derivatives

Reaction of sterically crowded achiral 3-(2-bromopropionyl)-2-oxazolidone derivatives with (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone in the presence of zinc dust in refluxing tetrahydrofuran was found to give the 1β-methyl substituted β-lactams as major products (at most, β:α=95:5). The major products were readily converted into the key intermediate of 1β-methylcarbapenems.