Treatment of mitomycin C (1) with the ambident nucleophile potassium ethyl monothiocarbonate (2) under reductive conditions (sodium dithionite) at approximately neutral pH at room temperature led to the formation of equivalent amounts of trans-(17) and cis-(18) aziridine ring-opened disubstituted mitosene adducts. In both cases substitution at carbons 1 and 10 proceeded with sulfur attack. The structural identity of each product was ...