The synthesis of miraziridine A, a pentapeptide derivative isolated from marine sponge, and its truncated analogs has been achieved. To construct the backbone of miraziridine A, a side- chain-unprotected vinylogous arginine was condensed with an aziridine-containing fragment prepared by a conventional solid-phase procedure. An analog lacking the vinylogous arginine site showed comparable inhibitory activity with miraziridine A, ...