Tetracyclic Alkaloids of the Matrine Group

Conformation 8 agrees with the chemical transformations of sophoridine obtained earlier (203). Matrine isomers are known to react faster by dehydrogenation over palladized asbestos or with mercuric acetate if they contain cis hydrogens. Sophoridine has been shown to dehydrogenate faster than allomatrine (5), but slower than matrine (4) (196). Since there are three cis hydrogens (H-5, H-6, H-7) in matrine and none in allomatrine, the sophoridine molecule is supposed to contain two cis hydrogens a cis orientation of H-6 and H-7 in 8 meets this requirement. 

On dehydrogenation with mercuric acetate, matrine, allomatrine, and sophoridine afforded the same dehydro product, 5-hydroxy-6,7-dehydromatrine (180) (196,203). The attachment of a hydroxyl group to C-5 and the double bond in the 6,7 position eliminate differences in the moleeular conformations of 4, 5, and 8. The absence of trans bands in the spectrum of 178 may be explained by isomerization taking place during reduction. 

Examination of Sophora alopecuraides L. sprouts led to the isolation of sophoridine Af-oxide as the main alkaloid (191,207). Later the A -oxide also was isolated from Euchresta japonica Benth. (40). Oxidation of sophoridine by m-chloroperbenzoic acid resulted in two A -oxides in a ratio of 1 5. The minor A -oxide was identical to the natural one, and its conformation corresponds to that of sophoridine (8). The other A-oxide (10) as suggested by H- and C-NMR spectra, appears to be the A-oxide of one of the labile conformations (38,39). 

Isomatrine was isolated from Sophora flavescens Ait. (79,208). There are absorption bands of a lactam group at 1620 cm and a rrani-quinolizidine at 2740, 2760, and 2780 cm in the IR spectrum. Heating of isomatrine (29) in aqueous solution with Pt02/H2 results in epimerization, and a mixture of matrine 

Albertidine, isolated from Leontice Albertii Rgl. (196,197), is a crystalline, optically active tribase. There are IR absorption bands for a trani-quinolizidine system at 2750 and 2793 cm and a six-membered lactam carbonyl at 1640 cm The absorption in the fingerprint region is similar to that of matrine. The mass spectrum of albertidine is characterized by ion peaks at miz 247 (M -1), 219, 205, 192, 177, 150, 137, 98, and 96 which are typical for matrine alkaloids (209). On the basis of spectroscopic data and taking into account the tranj-quinolizidine band in the IR spectrum, the probable structure 182, with rings A/B-trans, was proposed. 

---