1,2,5-Oxadiazolo[3,4-b]glycyrrhetinic acid

Abstract

The title compound [systematic name: 11-oxo-2,3-(oxydinitrilo)olean-12-en-29-oic acid], C30H42N2O4, contains a linear array of five six-membered rings and a five-membered heterocyclic ring. The C ring, containing an α,β-unsaturated ketone, has a slightly distorted half-chair conformation, as does the A ring, with N—C—C angles 125.3 (5), 111.2 (4), 124.9 (5) and 109.2 (5)°, while the other three six-membered rings adopt chair conformations. The enantiomer has been assigned by reference to unchanging chiral centres in the synthetic procedure. An intramolecular C—H...O interaction is present. In the crystal structure, intermolecular O—H...O hydrogen bonds link the molecules.