Configurational and conformational analyses of α-methylene-γ-butyro steroidal spirolactones

Abstract

The configurational and conformational analyses of α-methylene-γ-butyro steroidal spirolactones have been accomplished using 2D COSY, NOESY, ROESY and HETEROCOSY in conjunction with 1D ¹H 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 β and α dispositions, respectively, of the oxygen atom attached to the spirocentre.