title: 3β-Hy-droxy-lup-20(29)-en-28-yl 1H-imidazole-1-carboxyl-ate.
abstract: 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'-carbonyl-diimidazole (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 mol-ecules are O-H⋯O hydrogen bonded via the hy-droxy 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 mol-ecule gives values for bond-lengths and valency angles close to the experimental values. The calculations also reproduce the mol-ecular conformation well, with calculated puckering parameters that agree well with the observed values.
authors: R C
authors: RC
authors: Santos
authors: A
authors: A
authors: Matos Beja
authors: J A R
authors: JA
authors: Salvador
authors: J A
authors: JA
authors: Paixão
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