H-1-NMR SPECTRAL-ANALYSIS OF PHYSALIN-A, A 13,14-SECO-16,24-CYCLOSTEROID, BASED ON CRYSTAL-STRUCTURE OF (25R)-2,3,25,27-TETRAHYDROPHYSALIN-A DIMETHANOL SOLVATE

(25R)-2,3,25,27-Tetrahydrophysalin A dimethanol solvate, C30H42O12, a derivative of 13,14-seco-16,24-cyclosteroid physalin A, crystallizes in the orthorhombic space group P2(1)2(1)2(1), with a = 15.486(5), b = 14.794(4), 12.248(6) angstrom and Z = 4. The crystal structure has been solved by direct methods, and refined to an R-value of 0.053 for 2345 observed reflections. H-1 NMR spectral data of physalin A and its hydrogenated derivatives measured in dimethylsulfoxide-d6 solutions have been elucidated, based on the crystal structure of the tetrahydrophysalin A, enabling the assignment of all the proton signals of physalin A. The beta-proton of C(11)-methylene has been shown to resonate at remarkably higher field due to anisotropic shielding effect of carbonyl group at C(15).