Structure and Absolute Configuration of the 11-Noriridoid “Chapingolide”

Abstract

The natural product chapingolide {systematic name: (4aS, 7R, 7aR)-7hydroxy-7-(hydroxymethyl)-4,4a,7,7a-tetrahydrocyclopenta[c]pyran-3(1H)-one}, C9H12O4, (1), is a new 11-nor-iridoid isolated from Calatola mollis Standl. The colourless compound has a bicyclic structure with an endo double bond in the five-membered ring. The absolute configuration was established by mean of the anomalous dispersion of the oxygen scatters present in the structure. Calatola is a genus of trees in family Icacinaceae. To date, about seven Calatola species are recorded in America, and most of them are found in rain forest regions.1 Approximately, four species of Calatola plants were recorded in Mexico1 of which, Calatola mollis Standl is a tree up to 20 m tall. The seeds exhibited potently vomitive-purgative activity.2 At present Calatola mollis species had been poorly investigated with only botanical descriptions reported to date.1 Even thought, specimens of this species have been misidentified as Calatola costaricensis,1,3 and hence a phytochemical study of plants of Calatola genus will be useful to establish differences in secondary metabolites composition as a valuable systematic character. The chapingolide (1), a nor-iridoid, was obtained from the methanolic extract of the leaves of Calatola mollis Standl, as a crystalline colourless compound. Its bicyclic structure is closely related to the structures discussed in Valladares and Rios,4 and Franzyk and Stermitz.5 The main differences reside in the oxidation HETEROCYCLES, Vol. 91, No. 7, 2015 1417