Dihydropyran cycloadducts. Part 4. X-Ray and13C nuclear magnetic resonance studies on 2-methyl-9-phenyl-4a-pyrrolidin-1-yl-1,2,3,4,4a,-5,6,7,8,9a-decahydroxanthen

Abstract

Based on X-ray data the relative configurations in the title compound are as follows: the cyclohexane and dihydropyran rings are cis-fused and the 9-phenyl group is cis to the annelated hydrogen atom. This is the first evidence for previous assumptions that the ring closure of cyclic enamines with heterodiene systems results in a cis-ring junction. However, the position of the 9-phenyl group is in contrast to earlier results, established by 1H n.m.r. and chemical methods. The products from the reaction of different cyclic enamines with 2-benzylidenecyclohexanone show the same stereochemistry according to 13C n.m.r. investigations.