STRUCTURE AND ABSOLUTE CONFIGURATION OF THE 11-NORIRIDOID CHAPINGOLIDE

The natural product chapingolide {systematic name: (4aS, 7R, 7aR)-7-hydroxy-7-(hydroxyrnethyl)-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.