Structure and stereochemistry of some 1,2-disubstituted mitosenes from solvolysis of mitomycin C and Mitomycin A

Starting with mitomycin C (1), a number of solvolytic reactions were investigated and were found to result in opening of the aziridine ring with loss or migration of the 9a-methoxy group. A careful examination of the resulting 1,2-disubstituted 7-aminomitosenes indicated that there was a strong tendency for the azridine ring on opening to furnish mainly one stereoisomer, always with the oxygen stom at C-1 and the nitrogen atom at C-2. Thus the hydrolysis of 1withdition to small amounts of the trans-aminohydrin (10). Mitomycin A (2) BEHAVED ANALOGOUSLY. Both 1 and 2 generated a cis-1-acetoxy-2-acetamide when they were allowed to react with acetic anhydride. Acetolysis of mitomycin C was found to give the cis-1-hydroxy-2-acetamide (5), the trans-1-acetoxy-2-amine (14), and a cis-trans mixture of 1-acetoxy-2-acetamides (4 and 11, respectively). Routes to cis-1-methoxy-2-acetamide (9) were possible through the methanolysis of 1 or through the methylation of 5. For comparison, the trans-1-methoxy-2-acetamide (16) was obtained through a dnown resin-catalyzed methoxy migration from C-9A TO C-1 IN MITOMYCIN C. The use of 1-H nmr spectroscopy to asign configurations to 1,2-disubstituted mitosenes is discussed.