l-Proline derived nitrogenous steroidal systems: an asymmetric approach to 14-azasteroids

Abstract

An efficient chiral pool approach using L-proline to access 14-azasteroids under mild reaction conditions has been described. The key step involves the intramolecular S_N2′ cyclization reaction for the construction of critical C-ring in the nitrogen impregnated steroidal architectures bearing unsaturation at Δ⁹⁽¹¹⁾ position. In the endeavour to synthesize some new congeners, the remote electronic impact of the electron donating groups in A ring and heteroatoms like oxygen in B ring, on the propensity of C-ring cyclization was also observed.