METHYLENE-INDOLINES, INDOLENINES ET INDOLENIUMS-XIII; L'HYDROXY-16 DEHYDRO-1 VINCADIFFORMINE, INTERMEDIAIRE DANS LE REARRANGEMENT BIOMIMETIQUE DE LA VINCADIFFORMINE EN VINCAMINE

Article abstract of DOI:10.1016/S0040-4020(01)92453-6

The title compound is a crucial intermediate in the biomimetic conversion of vincadifformine 1 into vincamine 7.Its configuration at C-16 is established by a combination of chemical and spectroscopic evidence.Iodine oxidation converts 14 into the bridged lactam 18, thus proving a β configuration for the hydroxy group at C-16.The same reaction applied to vindoline 19 gives 21 identical with one of the compounds obtained by microbiological transformation of 19.The 13C NMR spectra of derivatives 3 and 8 (obtained by oxidation of vincadifformine) show that oxidation proceeds with introduction of the substituent at C-16, with a β configuration.The alcohol 3 however, posesses a different conformation due to strong hydrogen bonding with N-4.