International audienc

Caerulomycins produced by Streptomyces caeruleus, and collismycins more recently isolated from Streptomyces species, are bipyridinic molecules endowed with antibiotic and cytotoxic activities. The first syntheses of caerulomycin E (1), as well as new syntheses of caerulomycin A (2), are reported. Methodologies involving efficiently controlled reactions such as metalation and cross-coupling reactions have been developed from 2,2‘-bipyridine. The functionalization at C-6 could be achieved by metalation of 2,2‘-bipyridine N-oxides 5 and 12. 6-Halo-4-methoxy-2,2‘-bipyridines (6, 10, 11) became key-molecules of these different pathways, and further functionalization at C-5 allowed the first syntheses of collismycins A (3) and C (4).

The first synthesis of caerulomycin C (1), an antibiotic produced by Streptomyces caeruleus, is reported. This molecule, which exhibits a 2,3,4,6-tetrasubstituted pyridine structure, was prepared from 3,4-dimethoxypyridine in a five-step sequence. The methodology involves metalation, transmetalation, aromatic cross-coupling, and halogen migration reactions.