AN EFFICIENT CHEMICAL CONVERSION OF MITOMYCIN-A TO ISOMITOMYCIN-A

After inspection of the X-ray crystallographic analyses of mitomycin A (1a) and albomitomycin A (2), an efficient chemical conversion of 1a to isomitomycin A (3) via 2 was accomplished in 68% overall yield. First ta was converted to (8aS)-8a-bromoalbomitomycin A (4b) in 89% yield, which was reduced with tributyltin hydride and AIBN to give 2 in 85% yield. Second, the C4a-N4 bond of 2 was selectively cleaved under hydrogenolysis conditions, and subsequent air oxidation afforded 3 in 90% yield from 2. Treatment of 2 or 3 with NH3 in methanol afforded mitomycin C (1b) in good yield.