Process for intermediates to 1-carbapenems and 1-carbacephems.

摘要

A stereoselective process for chiral inter­mediates to 1-carbapenem and 1-carbacephalosporins is provided comprising the use of an N-acyl(4R)substituted-­1,3-thiazolidine-2-thione as a chiral auxiliary in boron enolate mediated aldol condensation with a protected-β-­keto ester aldehyde. Benzyl 3,3-(ethylenedioxy)-4-­formylbutyrate is condensed with the boron enolate formed with nbutyryl (4R)-methoxycarbonyl-1,3-thia­zolidine-2-thione to provide benzyl 3,3-ethylenedioxy-­(5R)-hydroxy-6-[(4R)-methoxycarbonyl-1,3-thiazolidine-­2-thione-3-ylcarbonyl]octanoate. Displacement of the thiazolidine-2-thione chiral auxiliary moiety with an O-alkyl, O-acyl or O-aralkyl hydroxyamine provides the corresponding chiral intermediate as the hydroxamate.