Is phototridachiahydropyrone a true natural product?

The occurrence of (-)-phototridachiahydropyrone (5) in nature has been proven. This compound has been now identified as minor component of the extract of marine sacoglossan mollusk Elysia crispata from which the main (-)-tridachiahydropyrone (4) was previously described. Synthetic (+/-)-5 was formerly obtained by Moses group by biomimetic photochemical conversion of (+/-)-tridachiahydropyrone (4). The same authors suggested that compound 5 had to be a natural product derived from precursor 4 yet to be discovered. Comparison of CD profiles of natural (-)-4 and (-)-5 indicated the same absolute configuration for both compounds. This evidence is in agreement with the concerted mechanism proposed for the photochemical conversion. (C) 2015 Sociedade Brasileira de Earmacognosia. Published by Elsevier Editora Ltda. All rights reserved.