C-13 NMR OF 4,5-EPOXY-3-SUBSTITUTED DECALIN AND ANALOGOUS DELTA(4)-OCTALIN DERIVATIVES - EPOXIDE-INDUCED AND METHYL-INDUCED SHIFTS

Fully assigned C-13 NMR chemical shifts for 4,5-epoxy-3-keto-, -3-hydr oxy-, and -3-acetoxydecalins and -10-methyldecalins, Delta(4)-octalins and 10-methyl-Delta(4)-octalins are reported together with epoxide- a nd methyl-induced shifts. The 4,5 alpha- and 4,5 beta-epoxydecalins pr esent epoxide gamma shielding in the A ring consistent in general with the syn-axial hydrogen rule. The 4,5 alpha- and 4,5 beta-epoxy-10-met hyldecalins present only slightly different shielding effects at gamma -carbons C-1, C-2, C-7, C-9 and C-11. Methyl-induced shifts in 4,5 alp ha- and 4,5 beta-epoxy-10-methyldecalins are similar at all carbons to those for trans- and cis-decalins (low temperature in the case of the latter), respectively, suggesting the predominance of the transoid an d cisoid A ring conformations, respectively, in these epoxides. The me thyl-induced shifts in the A ring of octalin analogues are intermediat e between those of the two epoxide configurational isomers. Epoxide ga mma-anti deshielding and gamma-syn shielding (analogous to those in 5- hydroxydecalins) are evident when comparison is made with C-13 shifts from analogous decalins, in contrast to the result when these effects are evaluated with data for Delta(4)-octalin analogues.