Several new alkalolds were isolated from Gardneria multiflora MAKINO (Loganiaceae) and structural elucidation of the six of them are presented. Alkaloids J (IX) and L (X) are trimethoxyoxindole alkaloids having a gardneramine (I) skeleton. The characteristic feature of these two alkaloids is their C-16-R configuration, which was proved by formation of the ether ring compound (XVI) on heating of IX or X in dilute hydrochloric acid. IX and X were derived from known bases, gardneramine (I) and 18-demethylgardneramine (III), respectively. Alkaloid N (XII) is also a trimethoxy oxindole alkaloid which has an α-glycol function at C-16 and C-17. This functionality was proved by the formation of an acetonide (XIX). The configurations of C-7 and C-16 in XII were determined by the generation of iminoether compound (XXI) via mesylate (XX). Gardneramine N-oxide (XIII), alkaloid M (XI), and exomethylene compound (XIV) were also isolated. Alkaloid I (V) also exists as a natural alkaloid. Alkaloidal constitution of Gardneria liukiuensis was also studied and was proved to be quite similar to that of Gardneria multiflora.
