Abstract
The methine base (X) derived from berberine chloride via several steps is photocyclized to the two isomeric carbinolamine forms (XI and XII) of 10b-methyl-4b, 10b, 11, 12-tetrahydrochelerythrine. Spectral data and chemical evidences reveal that the positions of the hydroxyl groups are C-6 in XI and C-4b in XII. The cis B/C ring juncture in XI is determined by observation of the nuclear Overhauser effect between 10b-Me and 4b-H. The formation pathways of XI and XII are examined and deduced to be the photoinduced intramolecular alkylation on carbon in the enamine system with olefin.
