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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.

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Nagarse, papain, pepsin and thermolysin were found to catalyze the peptide bond formation between two amino acids or peptides, one protected with a suitable group at the amino group and the other at the carboxyl group. Experiments with various combinations of amino acids and dipeptides show specificity in the catalytic action in varying degree which depending on the nature of the enzyme. Since the condensation takes place efficiently under mild conditions, this method opens up a useful way for the synthesis of peptides.