Directed Synthesis of Nonsymmetrical Bis‐Steroidal Pyrazines and the First Biologically Active Cephalostatin Analogues

Abstract

Thermolysis of vinylazides affords azirines that can be captured in situ with enamino ketones. This reaction sequence (see below) was developed into a new general method for the preparation of nonsymmetrical pyrazines and applied to the synthesis of cephalostatin analogues with high biological activity.