Bisnor-C-alkaloid

Of the numerous alkaloidal constituents ( 60) of the stem bark of Strychnos dolichothyrsa, six have so far been identified, including five bis-strychninoid ones 102 these are bisnordihydrotoxiferine, bisnor-C-curarine, bisnordihydrotoxi-ferine mono- and di-Xb-oxides, and (tentatively) bisnor-c-alkaloid D. 

Extracts of S. dolichothyrsa show marked muscle-relaxant activity, and contain a wide range (>60) of alkaloids. Bis-strychninoid alkaloids that are present include bisnordihydrotoxiferine, bisnor-C-alkaloid H, and caracurine Bisnordihydrotoxiferine is also found in the root bark of S. variabilis, together with strychnobiline (265), isostrychnobiline (266), and 12 -hydroxy-isostrychnobiline (267). As an internal carbinolamine ether, strychnobiline can be hydrolysed by acid to the component aldehyde and amino-alcohol, which are 18-deoxydiaboline and desacetylretuline since these bases also occur in 5. variabilis, the possibility that (265) is an artefact cannot be excluded. 

Lappaconine (11) is the first bisnor (C g) diterpene alkaloid to be found. The presence of the hydroxy-group on C-4 suggests that removal of C-19 is by a Baeyer-Villiger t q)e process. The biosynthesis of the lactone alkaloids such as heteratisine (137) also may involve such a step. 

The information to be gained from a mass spectrum is naturally dependent on structure. Serpentinine (253) gives an extremely complicated, worthless spectrum in which no molecular ion appears. The spectrum of C-curarine dichloride (54) shows only the molecular ion of the bisnor-base, while for calebassine dichloride (55) only the peaks corresponding to the loss of one and two molecules of water from the bisnor-base are observed. The other curare alkaloids also yield spectra which show a lack of fragment ion peaks they share this characteristic with strychnine. 

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