Tricyclic cephems as inhibitors of human leukocyte elastase. Furo[3,4-c]cepham sulfones

Furo[3,4-c]cepham sulfones were efficiently obtained from 1,1-dioxo-3-methylcephem-4-ketones. Cyclization improved at one time stability of the β-lactam towards hydrolytic cleavage (pH 7.4) and reactivity (second-order inhibition rate constant kon) towards human leukocyte elastase.