oa South African Journal of Chemistry - The alkaloids of the Leguminosae : part II2. Hofmann degradative studies on calpurnine from Calpurnia subdecandra
The axial configuration of the 13-hydroxyl group in 13-hydroxysparteine and hence 13-hydroxylupanine is confirmed by comparative rate studies on the hydrolysis of the acetate and of the epimeric acetate. Hofmann degradation of 13-hydroxylupanine methiodide gave a methine (II; R1 + R2=O, R3 = OH, R1 = H, R5 = CH3) and starting material. 13-Hydroxylupanine dihydromethine and 13-oxolupanine dihydromethine could not be degraded by the Hofmann reaction. The Hofmann degradation cannot therefore be used for the stepwise degradation of the D-ring in 13-hydroxylupanine.
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