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organic compounds
The two new triterpene lactones, 11α-hydroxy-28-methoxy-28-oxo-2,3-dinor-18β-olean-12-en-1,4-olide [C29H44O5.H2O, (5)] and 28-methoxy-28-oxo-1,2-dinor-10α,18β-oleano-9,12-dien-3,10β-olide [C29H42O4, (6)], were obtained by the method of Zaprutko [Pol. J. Chem. (1995), 69, 1003–1012]. In both compounds the lactone bridge connects atoms C4 and C10. In (5) the carbonyl group of the lactone bridge is formed by C1 and O1, and in (6) by C3 and O2. In (5) the methyl group at C10 has a β and in (6) an α configuration. The A and B rings are trans-fused in (5) and cis-fused in (6). The bond lengths in ring C indicate double bonds between C12—C13 in (5) and C9—C11 and C12—C13 in (6). The hydroxyl group at C11 in (5) is α oriented. Ring B in (5) has a chair conformation and in (6) a distorted half-chair conformation. Ring C in (5) has a sofa conformation and in (6) a slightly distorted half-chair conformation. Rings D and E have a chair conformation in both compounds and are cis-fused. The asymmetric unit of (5) contains one water molecule, disordered over two positions, making two alternative hydrogen bonds.
