Coupling process and intermediates useful for preparing cephalosporins

摘要

A process for the preparation of 3-cyclic-ether-substituted cephalosporins of formula I wherein the group CO₂R¹ is a carboxylic acid or a carboxylate salt and R² has the formula: wherein A¹ and A² have the meanings given in the specification by reacting compound of formula II: wherein R² is as defined above and R³ is para-nitrobenzyl or allyl with a compound R² L wherein R² is as defined above; and L is di-(C_1-6 alkyl)phosphorothioate in the presence of a solvent and a base.