CRYSTAL AND MOLECULAR-STRUCTURE OF 1-EPI-DELPHISINE AND NMR ASSIGNMENTS FOR DELPHISINE, 1-EPI-DELPHISINE AND DELPHININE

The crystal and molecular structure of the norditerpenoid alkaloid 1-e pi-delphisine (5), C28H43NO8, M(r)521.66, has been confirmed by as X-r ay diffraction study using the SIR 88 analysis program. The alkaloid c rystallizes in the space group P2(1) with cell parameters: a = 11.853( 1) angstrom, b = 10.511(1) angstrom, c = 11.854(1) angstrom, beta = 11 2.58(1), V = 1363.61(0) angstrom3, Z = 2, D(calc) = 1.27 g/cm3, lambda (Cu Kalpha) = 1.54184 angstrom, mu (Cu Kalpha = 7.2 cm-1, F(000) = 56 4, temperature 23-degrees-C, R = 0.052, for 2907 reflections. Ring A o f I-epi-delphisine exists in a chair conformation. By comparison, delp hisine which bears a C-I alpha hydroxyl group, has ring A in a boat co nformation stabilized by an intramolecular N - - - - H-O hydrogen bond . Ring D of both of these alkaloids exists in a boat form. Unambiguous proton and carbon-13 nmr assignments for delphisine, I-epi-delphisine and delphinine have been made by a detailed analysis of the DEPT, COS Y, HETCOR, COLOC, DIFNOE, and selective INEPT nmr techniques.