Synthesis of N‐Arylated Lactam‐Type Iminosugars by Cascade Radical Cleavage of α‐Amino Carbonyl Compound and Intramolecular Amidation

A metal‐free method is developed for the synthesis of N‐arylated lactam‐type iminosugars using hydrogen peroxide (35% in water) as an oxidant. The reaction of various α‐amino carbonyl compounds is performed in methanol, and the active methylene adjacent to the carbonyl group is rapidly removed to form a carboxylic acid as the key intermediate through a cascade radical cleavage reaction. Following an intramolecular amidation reaction, a series of N‐arylated lactam‐type iminosugars are prepared in satisfactory yields, providing an alternative protocol for the synthesis of such bioactive iminosugars. Additionally, several 4‐aminobutanamide derivatives are obtained by intermolecular amidation of the carboxylic acid intermediate.