Chemical Constituents from Dehaasia triandra. III. Bisbenzylisoquinoline Alkaloids from the Leaves and Their Conformational Analysis

Continuing investigation of the chemical constituents of Dehaasia triandra Merr. Provided from the leaves eleven bisbenzylisoquinoline alkaloids, homoaromoline (1), daphnandrine (2), aromoline (3), daphnoline (4), pangkorimine (5), colorflammine (6), thalrugosine (7), obamegine (8), 2-norobamegine (9), dehatridine (10), and 1,2-dehydroapateline (11). The complete assignment of the 1H- and 13C-nmr data of these alkaloids was accomplished by 1D and 2D analyses. Conformational analysis of these alkaloids was performed by computer-assisted dynamic calculations supplemented with NOED and NOSEY analyses. Stable conformations were characterized for both the type VI and type VIII of bisbenzylisoquinoline diphenyl ether ring linkages that explained some special features in their 1H-NMR spectra as well as their CD absorptions.