Studies of the Aconitine-type Alkaloids

The problem of the incorrect assignment of the structure of chasmanine based on the chasmanine-browniine-lycoctonine correlations (cf. vol. 6) was examined in view of these n.m.r. data. Complete assignments for all of the resonances for lycoctonine (56a) and browniine (56b) and their corresponding acetates were made. These data indicated that lycoctonine and browniine had identical stereochemistry in ring A, as have neoline and chasmanine. The reactions of the attempted browniine-chasmanine correlation would hot be expected to affect the oxygen function at C-1 it was therefore concluded that this work must be in error. 

As part of the n.m.r. study, the pyrodelphonine chromophore was examined. The unexpected u.v. absorption of pyrodelphonine (57) at A ax 245 m/z, 6300, which disappears upon acidification, was explained by Wiesner etal. to result from a cr-coupled TT-electron system between the nitrogen, the C-7—C-17 bond, and the TT-system of the C-8—C-15 double bond. They proposed an excited state resem- 

This work, with the earlier report by Jones and Benn, has established a n.m.r. data base for the aconitine- and lycoctonine-type alkaloids which should greatly facilitate structural investigations of new bases in these series. 

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