An α, β-unsaturated ketone alkylation and efficient reduction protocol for the synthesis of 3α-hydroxy-3β-methyl-4,4-dimethyl-5α-21-bromo-19-nor-pregnan-20-one

Abstract

Alkyl-substituted testosterone derivatives are promising platforms for new drug discovery in medicinal chemistry. This approach provides a simple and efficient method for introducing an alkyl substituent to steroids at the C-4 position. In this study, the novel compound 3α-hydroxy-3β-methyl-4,4-dimethyl-5α-21-bromo-19-nor-pregnan-20-one is synthesized from 19-nor-testosterone. The protocol involves methylation of the dienolate, reduction of the alkene, the Grignard reaction of the carbonyl group, a Wittig reaction, hydroboration with BH3, the oxidation and bromination with a 49% overall yield. For the methylation and reduction steps, the effects of the base, solvent, and reactant ratio on the conversion and yield are investigated. The structures of the synthesized compounds are determined by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) (electrospray ionization (ESI)).