Abstract
The structure (I) of a new alkaloid, corydalic acid methyl ester, mp 140-141°, [α]D+85.4°, C22H23O6N, isolated from Corydalis incisa PERS. (Papaveraceae) only in the vegetative stage, was established by the spectroscopic studies and chemical correlation with mesotetrahydrocorysamine. Furthermore, on the basis of the stereochemical investigation of mesotetrahydrocorysamine, the stereostructure of corydalic acid methyl ester was determined as XII. Corydalic acid methyl ester is a noteworthy natural alkaloid in which aromatic ring is attached to the position-3 of the tetrahydroisoquinoline, and biogenetically it is supposed to be derived from protoberberine skeleton by a fission of B-ring, possibly through an aldehyde-type intermediate.
