Two novel ansamitocin analogs from Actinosynnema pretiosum.

By using various column chromatography for purification, two new compounds of ansamitocin (1 and 2) were isolated from the extracts of fermentation broth of Actinosynnema pretiosum FIM06-0063. Their structures were established as maytansinol-9-methyl ether-3-propionate (1) and maytansinol-9-methyl ether-3-3'-methy-butyrate (2), respectively, by an extensive NMR analysis.