Dicarboxylic Acid Monoesters in β- and δ-Lactam Synthesis

A N-(2-methoxy-2-oxoethyl)-N-(phenylsulfonyl)glycine monomethyl ester of the respective dicarboxylic acid was involved in a reaction with imines promoted by acetic anhydride at an elevated temperature. Instead of the initially expected delta-lactam products of the Castagnoli-Cushman-type reaction, medicinally important 3-amino-2-azetidinones were obtained as the result of cyclization, involving a methylene group adjacent to an acid moiety. In contrast, replacing alcohol residue with hexafluoroisopropyl in the same substrate made another methylene group (adjacent to the ester moiety) more reactive to furnishing the desired delta-lactam in the Castagnoli-Cushman fashion.

Automated summary

In this study, a reaction between N-(2-methoxy-2-oxoethyl)-N-(phenylsulfonyl)glycine monomethyl ester and imines was promoted by acetic anhydride at an elevated temperature. Instead of the expected delta-lactam products, medicinally important 3-amino-2-azetidinones were obtained through cyclization reaction.