The Alkaloid Constituents of Euchresta japonica and the Stereochemical Assignment of Two Isomeric Sophoridine N-Oxides

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Nine known lupin alkaloids, (+)-matrine, (+)-matrine N-oxide, (+)-sophoranol, (+)-sophoranol N-oxide, (-)-sophoridine (1), (-)-cytisine, (-)-N-methylcytisine, (-)-N-formylcytisine, (-)-baptifoline, and (-)-sophoridine N-oxide (2a), were isolated from the aerial parts of Euchresta japonica BENTH., in addition to two alkaloids, (+)-5,17-dehydromatrine N-oxide and (-)-12-cytisineacetic acid, reported previously. 2a was one of the two diastereoisomeric sophoridine N-oxides with different configurations of N-oxide nitrogen. Seasonal variations of the alkaloid contents in the aerial and ground parts of E. japonica were also examined. The N-oxidation of sophoridine with m-chloroperbenzoic acid gave two N-oxides in a ratio of ca. 1 : 5. The minor N-oxide was identical with 2a. The major N-oxide (2b) was characterized as the other diastereomer of sophoridine N-oxide by MS spectroscopy and deoxygenation to sophoridine. The stereochemical assignments of the two isomers were carried out by analysis of their ^1H- and ^<13>C-NMR spectra.
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1980-02-25