Chaparrin, the bitter principle from

Davidson, Thomas A.; Hollands, T. R.; Mayo, P. De

doi:10.1016/s0040-4039(00)70965-8

Cited by 14 publications

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“…Although there were originally minor differences in the characterization, essentially similar conclusions had been reached. Further degradative work was then continued with exchanges of information between the two groups resulting, by different means, in the same gross structural conclusions (1,4).…”

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Terpenoids: Xii. The Structure of Chaparrin

Davidson¹,

Hollands²,

Mayo³

et al. 1965

Can. J. Chem.

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Chaparrin, the bitter principle from Castela nicholsonii may be dehydrated in two stages to give the partially aromatized substance chaparrol. By further stepwise degradation the latter has been converted to the dihydrophenanthrene ( S I I I ) which allows the assignment of structures XVII and I to chaparrol and chaparrin respectively.In 1922 Bosman (2) reported the isolation, from Castela nicholsonii Hook (Chaparro amargosa), of two bitter substances, castelin and castelamarin. In view of the improbable nature of the structure (the lactone of 2-hydroxy-3-methox~~cyclohexaneacetic acid) proposed for one of these, a reinvestigation seemed called for. However, an attempt to isolate either of these substances failed. Instead, a new and apparently unrelated compound was obtained and characterized. While it was under investigation the isolation of the same substance was reported by Geissman and Chandorkar (3). Although there were originally minor differences in the characterization, essentially similar conclusions had been reached. Further degradative work was then continued with exchanges of information between the two groups resulting, by different means, in the same gross structural conclusions (1, 4).I t is the purpose of this report to present our results leading to the selection of formula I a s the representation of the constitution of chaparrin. Our results leading to the elucidation of the stereochemistry and absolute stereochemistry of this substance together with those of chaparrol and its isomers neochaparrol and isochaparrol will be presented in the following paper in this series.Chaparrin, best isolated (see Experimental) as the acetate mixture, forms a tri-and a tetraacetate froin which chaparrin can be recovered on alkaline hydrolysis. Since chaparrin has the forinula C30H28Oi three oxygen atoms remain to be accounted for.Of these, two must be present in a lactone. Thus, although chaparrin will dissolve in aqueous alkali and is precipitated from the alkaline solution on acidification i t shows, itself, 'Part of the ?naterial here described wasjirst presented in preliminary forvz (1).

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