Total synthesis of pikromycin.

The total synthesis of pikromycin (6), the first isolated macrolide antibiotic, was achieved. The target macrolide was retrosynthetically divided into two parts, pikronolide (6a) (aglycon) and D-desosamine. The aglycon was synthesized using key reactions such as an asymmetric aldol reaction, Yamaguchi esterification, and ring-closing metathesis. The aglycon was coupled successfully with the trichloroacetimidate derivative of D-desosamine under Lewis acidic conditions to afford pikromycin. Narbomycin (5) was also synthesized from narbonolide (5a) under identical conditions.