Synthesis of steroid intermediates via alkylation of dianion derived from acetoacetic ester

A synthetic route for A-ring aromatic steroid intermediates starting from alkylation of dianion derived from acetoacetic ester with m-methoxyphenylethyl bromide to form benzene ring connected to a linear six-carbon fragment is described. This unit, after chemical modifications to 5, was condensed with 2-methylcyclopentan-1,3-dione (6a) to form prochiral trione, 7a, a key synthetic intermediate in A-ring aromatic steroid. Microbial reduction of 7a with Schizosaccharomyces pombe (NRRL Y-164) gave chiral (-)-11 in 65% yield. Starting from 2,2-dimethylsuccinic acid, 2,4,4-trimethylcyclopentan- 1,3-dione (6a) was prepared, which was condensed subsequently with 5 to form racemic 7b trione intermediate. Asymmetric cyclization of 7b in the presence of l-(-)-phenylalanine, followed by acidic cyclization led to regiospecific synthesis of 16,16-dimethyl tetracyclic steroid intermediate.