In 2004, a new anti-HIV alkaloid named drymaritin was isolated from Drymaria diandra. The authors identified the alkaloid as 5-methoxycanthin-4-one on the basis of spectroscopic data. Here we describe a synthetic approach that unambiguously gave 5-methoxycanthin-4-one, but the synthetic product showed spectroscopic data significantly different from those of the Drymaria alkaloid. Extensive re-evaluation of the spectroscopic data published for this and related alkaloids has led to the conclusion that drymaritin does not have a canthin-4-one backbone, but is identical to the known alkaloid cordatanine (4-methoxycanthin-6-one).