Structural Elucidation of Murrafolines, Six Novel Binary Carbazole Alkaloids Isolated from Murraya euchrestifolia

In previous studies on the chemical constituents of Murraya euchrestifolia hayata(Rutaceae) collected in Taiwan, we preliminarily reported the first isolation and structure of a binary carbazole alkaloid, murrafoline-A (1). Since then, the isolation and spectroscopic structural elucidation of three new binary carbazoles, murrafoline-B (2), -C (5), and -D (3), have been reported. This paper describes in detail the structural elucidation of these novel binary carbazole alkaloids and also introduces two additional ones, murrafoline-G (4) and -H (6). Treatment of a mixture of girinimbine (7) and murrayafoline-A (8), which are monomeric carbazoles and structural components of murrafolines, with Nafion 117, an acidic perfluorinated ion-exchange resin, was found to produce murrafoline-D (3), -G (4), and -H (6).