Some 8-substituted derivatives of the protoberberine alkaloids palmatine (1a) and berberine (1b) have been prepared and investigated by 1D and 2D NMR spectroscopy (H-1, C-13, N-15). Complete NMR data for the 8-hydroxy (2), 8-methoxy (3), 8-ethoxy (4), and 8-trichloromethyl (5) 7,8-dihydro derivatives of 1a and 1b, as well as X-ray data for 8-methoxydihydroberberine (3b), 8-trichloromethyldihydropalmatine (5a), and 8-trichloromethyldihydroberberine (5b), are presented. The physicochemical data for all of these compounds are reviewed and compared with previously published values.
The title compound [systematic name: 9,10-dimethoxy-2,3-methylenedioxy-5,6-dihydrodibenzo[a,g]quinolizinium formate-succinic acid (1/1)], C(20)H(18)NO(4)(+).CHO(2)(-).C(4)H(6)O(4), contains centrosymmetric pairs of almost planar berberine cations, and hydrogen-bonded (C(4)H(6)O(4).HCOO(-))(2) rings of succinic acid with formate anions, bonded by O-H...O hydrogen bonds with O...O distances of 2.4886 (15) and 2.5652 (16) A. Pairs of cations and molecules of succinic acid are connected by non-conventional weak C-H.O hydrogen bonds, with C...O distances of 3.082 (2) and 3.178 (2) A.
Adducts of the quaternary protoberberine alkaloids (QPA) berberine, palmatine, and coptisine were prepared with nucleophiles derived from pyrrole, pyrazole, imidazole, and 1,2,4-triazole. The products, 8-substituted 7,8-dihydroprotoberberines, were identified by mass spectrometry and 1D and 2D NMR spectroscopy, including (1)H--(15)N shift correlations at natural abundance. In addition, two adducts of QPA with chloroform and methanethiolate were characterized by using NMR data. Single-crystal X-ray structures of 8-pyrrolyl-7,8-dihydroberberine, 8-pyrazolyl-7,8-dihydroberberine, and 8-imidazolyl-7,8-dihydroberberine are also presented.
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