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

The title triterpene, C34H52N2O3, 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.

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