J. Le Men

Méthylène-indolines, indolénines et indoléniniums—XIII: L'hydroxy-16 déhydro-1 vincadifformine, intérmédiaire dans le réarrangement biomimétique de la vincadifformine en vincamine

Abstract 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 13 C 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.

Methylene-indolines, indolenines et indoleniniums—XII : Hemisynthese de la dehydro-14,15 vincamine et de la criocerine

Resume (-)-Tabersonine 1 was oxidised and rearranged to (+)-14,15-dehydrovincamine 5, (+)-14,15-dehydro,16-epi vincamine 6, and the rhazinilam derivative 9. Iodine and potassium iodate oxidised 5 to 14-iodo criocerine 13, Which led to criocerine 14.

Alcaloïdes du Pandaca ochrascens

Abstract From leaves and root bark of Pandaca ochrascens ten alkaloids were isolated: apparicine, akuammicine, dehydro-19,20 condylocarpine, akuammidine, epi-16 dehydro-14,15 vincamine, ibogaine, iboluteine, ibogaline and also two new alkaloids, epi-19 ibogaine or (19R) 19-hydroxyibogaine and epi-19 iboxygaline or (19R) 19-hydroxyibogaline. The absolute configuration at C19 of these new alkaloids and other alkaloids hydroxylated on 19 of the Iboga type is discussed.

Alcaloïdes des feuilles et écorces de tronc d'Alstonia odontophora

Abstract Six known indole alkaloids were isolated from the leaves and stem bark of Alstonia odontophora : vincamajine, 11-methoxy- akuammicine, quebrachidine, pleiocarpamine, antirhine, pleiocorine and pleiocraline, along with the novel bisindole, N (I′)-demethylpleiocorine.

Derives 14-hydroxyles de la vincadifformine et de la vincamine

Abstract Hydroboration-oxidation of tabersonine 1 yielded as major product 14 β-hydroxy vincadifformine 9b, which was correlated with 14 β-hydroxy N(1)-methyl 2β-H, 16β-H dihydro vincadifformine 6b (previously prepared and characterised), and 14α-hydroxy vincadifformine 9a as minor product. The regio- and stereoselectivity of hydroboration-oxidation were interpreted. 9a and 9b were respectively oxidised and rearranged to the corresponding 14-hydroxy vincamines 13a and 13b. The coupling constants of H(14) on the NMR of the acetyl derivatives of 9a, 9b, 13a and 13b are consistent with an inversion of N(4) during the rearrangement leading from the vincadifformine to the vincamine skeleton.

Alcaloides du Strychnos variabilis

Abstract The structures of two new dihydroindole alkaloids have been elucidated by chemical correlations with akuaammicine for (−)2β,16β- dihydroakuammicinol and strychnine for (+)Na-acetyl-2β,16α-dihydroakuammicinal.

Alcaloïdes des écorces de tronc et des écorces de racine de L'Hunteria elliotii

Abstract Nine known indole alkaloids were isolated from the stem and root barks of Hunteria elliotii : aspidofractinine, eburnamenine, eburnamine, isoeburnamine, eburnamonine, kopsinine, pleiocarpamine, quebrachamine and vincadifformine, along with o -ethyleburnamine.

Structure des caboxines: Alcaloïdes oxindoliques du Cabucala fasciculata

Abstract The structures of three new 11-monomethoxy pentacyclic oxindole alkaloids have been elucidated by chemical correlations with reserpinine: caboxine-A was assigned to the allo C 19 -methyl α series: 3 S , 4 R , 7 S , 19 S ; isocaboxine-A and B to the epi - allo C 19 -methyl α series and have, respectively, the following configurations 3 R , 4 S , 7 S , 19 S and 3 R , 4 S , 7 R , 19 S .

Structure de la Pandoline : Nouveau type d'alcaloide indolique

Resume La structure de la pandoline : (+) hydroxy 20ψ ψ- vincadifformine, est confirmee au moyen de deux correlations chimiques avec la (+) catharanthine.