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-(-)-phenylanlanine, followed by acidic cyclization led to regiospecific synthesis of 16,16-dimethyl tetracyclic steroid intermediate.[1]References
- Synthesis of steroid intermediates via alkylation of dianion derived from acetoacetic ester. Wang, K.C., Liang, C.H., Kan, W.M., Lee, S.S. Bioorg. Med. Chem. (1994) [Pubmed]
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