Irlstitrrtefo~. Ntrtionol P~.orirrcls Rc~c,rr1.c11 o11d the, Dcpcirtme~rt of Clic,tnist~:~, Urlicusiry of Gro~.girr, Atllens, GA 30602, U.S.A.Received December 15, 1978 S. WILLIAM PELLETIER, NARESH V. MODY, and RAJINDER S. SAWHNEY. Can. J. Chem. 57, 1652 (1979).The natural abundance carbon-13 nuclear magnetic resonance spectra of some C19-diterpenoid alkaloids and their alkamines (lappaconitine, lappaconine, lapaconidine, ranaconine, 14-dehydrobrowniine, aconine, pseudoaconine, deoxyaconine, and hypaconine) have been determined at 15.03 MHz. With the aid of proton decoupling techniques, additivity relationships, and comparison with spectra of related alkaloids, self-consistent and unambiguous assignments of nearly all carbon resonances for these alkaloids have been made. Some important chemical shift trends have been observed, which are useful for identifying the basic C19-diterpenoid alkaloid skeleton and the hydroxy and methoxy group substitution patterns in these alkaloids. On the basis of 13C nrnr spectra of lappaconitine and lappaconine, the anthranoyl ester moiety is assigned to the C-4 position in lappaconitine. The 13C nrnr spectra of lapaconidine, aconine, and pseudoaconine taken in pyridine and chloroform have been compared to determine the conformational changes of the ring A hydroxy groups in these alkaloids.
S. WILLIAM PELLETIER, NARESH V. MODY et RAJINDER S. SAWHNEY. Can. J. Chem. 57, 1652 ( 1979).Operant a 15.03 MHz, on a determine les spectres rmn du 13C en abondance naturelie de quelques alcaloi'des diterptnoi'des en C19 et de leurs alkylamines (Iappaconitine, lappaconine, lapaconidine, ranaconine, dehydro-14 browniine, aconine, pseudoaconine, deoxyaconine e t hypaconine). Faisant appel aux techniques de decouplage des protons, a des rkgles d'addition et a des comparaisons avec les spectres d'alcaloi'des apparentts, on a pu proposer des attributions autocoherentes et non ambigiies de pratiquement toutes les resonances, de carbones de ces alcaloi'des. On a observe quelques tendances importantes des deplacements chimiques qui sont utiles pour identifier le squelette fondamental des alcaloi'des diterpknoi'des en Cl9 ainsi que la disposition des groupes hydroxyles et mtthoxyles attaches a ce squelette. En se basant sur les spectres rmn du 13C de la lappaconitine et de la lappaconine, on attribue la position ester anthranoyle a la position C-4 de la lappaconitine. On a compare les spectres rmn du 13C de la lapaconidine, de I'aconine et de la pseudoaconine, dCterminCes en solution dans la pyridine et le chloroforme, pour evaluer les changements conformationnels du groupe hydroxyle attache au cycle A de ces alcaloi'des.[Traduit par le journal]
