CONSTITUTION, STEREOCHEMISTRY AND CONFORMATIONAL BEHAVIOR OF THE PHOTOREACTION PRODUCT OF 7-DEACETOXY-7-OXOKHIVORIN

By means of 2D NMR experiments (COSY, HMQC, HMBC, ROESY), the constitu tion of the photoreaction product 3-deoxo-1 alpha,3 alpha-diacetoxy-1, 2,3,3,8,30-hexahydro-18 beta H (2), obtained by photolysis of 7-deacet oxy-7-oxokhivorin (1) in methanol, was shown to be a ring B seco-limon oid with the 14,15-epoxide intact. The configuration of C-8 is R. Ring C adopts a twist-boat conformation. No conformational preferences for the rotation of ring A in 2 with respect to rings C/D and for the sid e-chain C-6/C-7 could be detected. Nearly all H-1 and all C-13 resonan ces were assigned unambiguously. (C) 1998 John Wiley & Sons.