3β-Hy­droxy­lup-20(29)-en-28-yl 1H-imidazole-1-carboxyl­ate

The title triterpene, C(34)H(52)N(2)O(3), is a C-28 carbamate derivative of betulin prepared in a one-step reaction from the commercially available 1,1′-carbonyl­diimidazole (CDI). All rings are fused trans. The X-ray study shows the retention of the configuration of C-28 with respect to the known chiral centres of the molecule. In the crystal, the mol­ecules are O—H⋯O hydrogen bonded via the hy­droxy group and the carbonyl group of the carbamate function into chains running along the c axis. A quantum-mechanical ab initio Roothaan Hartree–Fock calculation of the equilibrium geometry of the isolated mol­ecule gives values for bond-lengths and valency angles close to the experimental values. The calculations also reproduce the mol­ecular conformation well, with calculated puckering parameters that agree well with the observed values.