Ansa macrolide M 16 M 16 MAYTENUS CELESTRACAE (B631179K404) Maytansine, 2'-de(acetylmethylamino)-22-demethyl-2'-[[(1,2-dimethylcyclopropyl)carbonyl]methylamino]- Maytansine, N2'-deacetyl-22-demethyl-N2'-[(1,2-dimethylcyclopropyl)carbonyl]- NSC269762