Antitumor principles in mosses: the first isolation and identification of maytansinoids, including a novel 15-methoxyansamitocin P-3.

A novel 15-methoxyansamitocin P-3 [2], in company with three known maytansinoids 1, 3, and 4, was isolated for the first time from two Japanese mosses, Isothecium subdiversiforme and Thamnobryum sandei. All are potent cytotoxic compounds.