Covalent bonding of azoles to quaternary protoberberine alkaloids.

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.

Berberine formate-succinic acid (1/1).

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.

Palmatine and berberine isolation artifacts.

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.