STRUCTURE, ABSOLUTE-CONFIGURATION, AND CONFORMATION OF A FUSED COMPLEX CYCLIC CARBOHYDRATE FROM A CAMEROON PLANT-EXTRACT (CAMT2)

The crystal and molecular structure of the natural product C29H38O9, a n extract from a Cameroonian plant, has been determined by direct meth ods. Crystals are orthorhombic, P2(1)2(1)2(1), a = 24.571(4), b = 16.3 98(3), c = 13.778(4)Angstrom, Z = 8, D-c = 1.270 mg/m(3). The final R- factor for 2892 reflections with I > 2 sigma(I) is 0.0531. The two mol ecules forming the asymmetric unit have very similar molecular geometr y, each molecule comprising a nucleus of six fused rings B to G: where B = pyranyl, C = pyranyl, D = furanyl, E = cyclohexene, F = pyranyl, G = cyclohexyl. Ring B also has a furanyl side-group (ring A). The rin g conformations in both molecules are: A (1/2-chair/envelope); B(envel ope); C(envelope); D(1/2-chair); E(1/2-chair); F(envelope); G(chair). In the cyclohexene ring E the substitution pattern is 2-hydroxy 3-meth yl 5-dimethyl. The two molecules in the asymmetric unit are linked by two OH O hydrogen bonds to form the crystal structure.