Configurational and conformational analyses of alpha-methylene-gamma-butyro steroidal spirolactones

Abstract

The configurational and conformational analyses of alpha-methylene-gamma-butyro steroidal spirolactones have been accomplished using 2D COSY, NOESY, ROESY and HETEROCOSY in conjunction with 1D H-1 NMR. The analyses indicate that the major or the only spirolactones formed at positions 2, 3 and 6 of the steroids have the steroidal ring bearing the spirolactone in a chair conformation with an axial disposition of the oxygen atom attached to the spirocentre. The corresponding minor spirolactones have equatorial configurations. Steroids with spirolactones at positions 16 and 17 have beta and alpha dispositions, respectively, of the oxygen atom attached to the spirocentre.