Alkaloids of Delphinium bicolor Nutt

Alkaloids of Delphinium bicolor Nutt.—The structures of alkaloids A and B have been established by an X-ray crystallographic analysis of the hydroiodide salt of alkaloid A and its chemical conversion into alkaloid B.10 These compounds were originally assigned structures (16) and (17), respectively.11 On the basis of extensive 13C n.m.r. studies,12 the structures of these compounds were revised to (18) and (19), respectively. However, the X-ray crystallographic structure determination of the hydroiodide of alkaloid A revealed that it is the 6/3-epimer of (18), i.e. (20).10 The incorrect assignment from the n.m.r. data resulted from an incorrectly drawn structure for the compounds with which the 13C n.m.r. signals had been correlated. 

On heating alkaloid A (20) with 3M sulphuric acid on a steam bath overnight, alkaloid B (21) was obtained. 

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Alkaloids of Delphinium bicolor Nutt.—The structure of Alkaloid A from this plant has been revised on the basis of additional 13C n.m.r. data.24 Alkaloids A and B formerly had been assigned structures (23) and (24), respectively, as a result of a pyrolysis study of Alkaloid A and from 13C n.m.r. data.25 Comparison of the spectra of these alkaloids with those of neoline (10), 8-acetylneoline (25), delphisine (12), trimethoxyneoline (26), heteratisine (27), and 6-acetylheteratisine... 

Structure [554] has been assigned to alkaloid A from Delphinium bicolor Nutt, from a comparison of its 13C NMR spectrum with the... 

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