Formal total syntheses of isodelphinine (3) and penduline (50) was achieved. Isodelphonine (19), an alkamine of 3, was synthesized by the following two routes from chasmanine (1), which had already been synthesized by Wiesner et al. Des-N-ethyl-diacetylchasmanine (8) was derived from 1 by the known method, and des-N-ethyl-N-formyl-14-acetyl-8, 15-epoxychasmanine (12) was synthesized via intermediates, des-N-ethyl-N-formyl-diacetylchasmanine (9) and des-N-ethyl-N-formyl-8, 15-dehydro-14-acetylchasmanine (10). Des-N-ethyl-N-formyl-14-acetyl-15-hydroxychasmanine (16) was obtained by epoxy-ring opening reaction of 12. LiAIH
4 reduction of 16 gave rise to 15-epi-isodelphonine (17), whose structure was confirmed by X-ray analysis, so that the introduced C
15-OH group of 16 was β configuration. In order to invert this C
15-OH group, oxidation-reduction procedure was used. Des-N-methyl-N-formyl-14-acetyl-15-dehydroisodelphonine (18) was obtained by Swern's oxidation of 16. LiAIH
4 reduction of 18 gave rise to isodelphonine (19) and 15-epi-isodelphonine (17). Thus we have succeeded in the introduction of 15-α-hydroxy group into chasmanine (1). The improved route to isodelphonine (19) was also studied. Compound (8) was methylated to give des-N-ethyl-N-methyl-diacetylchasmanine (42). Pyrolysis of 42 gave des-N-ethyl-N-methyl-8, 15-dehydro-14-acetylchasmanine (43), which was oxidized with OsO
4 to give 14-acetyl-15-epi-isodelphonine (44). Compound (44) was also oxidized by Swern's method to give 14-acetyl-15-dehydro-isodelphonine (45). Reduction of 45 with LiAl (OCH
3)
3H at -70°C gave rise to isodelphonine (19) exclusively. And then, isodelphinine (3) was derived from isodelphonine (19) via intermediates, 14-benzoylisodelphonine (46), 14-benzoyl-15-trichloroethoxycarbonyl-isodelphonine (48) and 8-acetyl-14-benzoyl-15-trichloroethoxycarbonyl-isodelphonine (49). Penduline (50) was also synthesized from chasmanine (1) by use of the latter method.
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