Revision of the Structure of Strychnochromine

The structure of strychnochromine, an unusual alkaloid isolated from a new batch of the root bark of Strychnos gossweileri has been revised . To confirm the indoline structure ( proposed in 1988) and to establish the stereochemistry of the compound extensive 2D-NMR experiments were carried out. The COSY experiments mostly confirmed the previous observations but the COLOC maps did not fit the first proposed structure!The problem was solved by single-crystal X-ray analysis of the p-bromobenzoyl ester of strychnochromine. The new structure, with its tetrahydroquinoline ring, is very unusual in Strychnos species but the formation of quinolines from indole alkaloids has already mentioned in some other plants ( Cinchona, Alstonia, Hunteria..).