Synthesis of (g1n) Thz (la) by a Hantzsch synthesis (Scheme 11), involving reaction of an appropriate optically active thioamide and ethyl bromopyruvate, was considered the route of choice. The only real uncertainty involved whether or not optical integrity could be preserved. With ZLG~ u (2) as starting material the required thioamide (9) was prepared by the method summarized in Scheme I. In agreement wit, h previous results" conversion of ...
