Stereocontrolled synthesis of 2-aryl tetralones. Application in the synthesis of B/C hexahydrobenzo[c]phenanthridine alkaloids

Hexahydrobenzo[c]phenanthridines possessing a B/C cis ring junction have be en synthesized in a stereoselective way starting from chiral non-racemic 2- aryl-tetralones prepared by asymmetric alkylation of (+)-(S,S)-pseudoephedr ine based arylacetamide enolates with appropriately functionalized 2-aryl-1 -iodoethane electrophiles. Subsequent transformations (intramolecular Fried el-Crafts acylation, stereocontrolled reductive amination and Pictet-Spengl er cyclization) yielded the target heterocycles in good overall yields and in excellent stereoselectivities. (C) 2000 Elsevier Science Ltd. AU rights reserved.