Synthesis of benzo[c]quinolizin-3-ones: Selective non-steroidal inhibitors of steroid 5α-reductase 1

A short and efficient synthesis of novel benzo[c]quinolizin-3-one derivatives is described. The synthesis is based on the tandem Mannich-Michael cyclization between 2-silyloxy-1,3-butadienes and a N-t-Boc iminium ion. The prepared derivatives are selective inhibitors of human steroid 5α-reductase isoenzyme 1, thus having potential application as drugs for treatment of male pattern baldness and other DHT-dependent skin disorders.