A Versatile Synthesis of 1,1-Dioxo 7-Substituted Cephems: Preparation of the Human Leukocyte Elastase (HLE) Inhibitor 1,1-Dioxo-trans-7-methoxycephalosporanic Acid tert-Butyl Ester

Article abstract of DOI:10.1021/jo00277a030

A four-step synthesis of the human leukocyte elastase (HLE) inhibitor 1,1-dioxo-trans-7-methoxycephalosporanic acid tert-butyl ester in 44percent isolated yield from 7-aminocephalosporanic acid (7-ACA) is described.A variety of 7-substituents have been introduced via metal-catalyzed diazo insertion reactions, and the use of a flow reactor for chemodiscriminate control of particularly rapid reactions is presented.A chemoselective oxidation of 7-ACA tert-butyl ester to the corresponding 1,1-dioxide without formal N-protection is introduced.