Abstract
Aldol condensation of the lithium enolate of 2 with m-methoxyphenylacetaldehyde afforded 3a and 3b with good erythro stereoselectivity (5:95). Acid catalyzed cyclization of 3a gave the tetrahydrophenanthrene 5 while 3b yielded the 3-oxobicyclononanones 6. A mechanism is discussed to account for the derived products and a detailed 1H NMR structural analysis of the [3.3.1] bicyclic systems is utilized to indirectly characterize the threo and erythro alcohols 3a and 3b .