15-Methoxymaysine 4,24-Dioxa-9,22-diazatetracyclo(19.3.1.1(10,14).0(3,5))hexacosane, maytansine deriv. 78987-29-8 B820915K136 Maytansine, 3-de[2-(acetylmethylamino)-1-oxopropoxy]-2,3-didehydro-15-methoxy-, (2E)- NSC354641 TWEWSINE (B820915K136) Trewsine