SPECTROSCOPIC ELUCIDATION OF GLYCOBISMINES, 1ST NATURALLY-OCCURRING BINARY ACRIDONE ALKALOIDS CONTAINING A CARBON CARBON LINKAGE

The structures of glycobismine-A 1, -B 4 and -C 4', novel binary acridone alkaloids, from Glycosmis citrifolia (Willd.) Lindl. (Rutaceae) have been elucidated by spectroscopic studies using H-1-C-13 long-range COSY and/or HMBC experiments. In a preliminary communication we reported the structure of glycobismine-A 1 as the first naturally occurring binary acridone alkaloid having a carbon-carbon linkage. This paper deals with the complete and detailed spectroscopic structural elucidation of compound 1 and the structures of two additional new binary acridone alkaloids, glycobismine- B 4 and -C 4'.