Process for preparing carbapenem compounds

摘要

Novel amino acid derivatives of the formula <IMAGE> wherein R1 is a protecting group removable under reducing or acid conditions, and R2 and R5 are hydrogen or carboxylic protecting groups, are useful as intermediates in preparing stereospecific carbapenam/carbapenem derivatives. R1 is removed under reducing conditions to form a pyrrolidine derivative, which is further cyclized from the R5=H compound to form a beta -lactam ring. Stereospecificity at the 6-position is achieved by treatment with lithium diisopropylamide (LDA) and quenching at different temperatures. Compound (I) can be prepared by treating R1-protected R3-pyrrolidone carboxylic acid R2-ester with a lithium enolate of the formula R4CHLiCO2R5. The lithium enolate can be formed from R4CH2CO2R5 by treatment with LDA.