title: 1,2,5-Oxadiazolo[3,4-b]glycyrrhetinic acid.
abstract: THE TITLE COMPOUND [SYSTEMATIC NAME: 11-oxo-2,3-(oxy-dinitrilo)olean-12-en-29-oic acid], C(30)H(42)N(2)O(4), 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 enanti-omer 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, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules.
authors.affiliation: Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.forename: Libing
authors.initials: L
authors.lastname: Yu
authors.forename: Ruji
authors.initials: R
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Ju