Revised Structure of the Alkaloid Drymaritin

Abstract

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).

Structural Revisions of Natural Products with the Aid of the Structure Elucidator System

“…We agree with the authors, 28 theoretically be avoided. This example also convincingly shows that 13 C chemical shift calculation and dereplication of any isolated natural product are very useful as the first steps towards structure identification.…”

“…In this case, no chemical synthesis would be necessary to disprove structure 12.14. Structure 12.14, which was synthesized by Wetzel et al, 28 was also confirmed by strict structure generation (no NSCs) from the 2D NMR data 28 with the following results: k ¼ 4083-3874-1439, t g ¼ 12 min 6 s. The first ranked structure coincided with structure 12.14.…”

“…This alkaloid showed interesting anti-HIV activity and has been mentioned in a series of review articles dealing with bioactive natural products. 28 In 2009 Wetzel et al 28 revised structure 12.14. They synthesized 5-methoxycanthin-4-one and discovered that the synthetic product displayed spectroscopic data significantly different from those of the drymarietin alkaloid.…”

“…Wetzel et al 28 comment in the conclusion of their article that their results ''demonstrate that structure elucidations based only on spectroscopic data bear some risks of misinterpretation'' and that ''efforts regarding the total synthesis of alkaloids (performed sine ira et studio) helped to identify an erroneous structure assignment''. We agree with the authors, 28 theoretically be avoided.…”

Total synthesis of cordatanine, structural reassignment of drymaritin, and anti-inflammatory activity of synthetic precursors

“…1). 2 Based on our long-term interest in canthin-6 -one, this reassignment drew our attention. Herein, we synthesized cordatanine unambiguously by a four-step procedure to validate the exact structure.…”