Stereoisomerism of the matrine alkaloids

IR and Vibrational Circular Dichroism Spectroscopy of Matrine- and Artemisinin-Type Herbal Products: Stereochemical Characterization and Solvent Effects

“…It has four stereogenic carbon centers at C-5, C-6, C-7, and C-11 and two nitrogen stereogenic centers at N-1 and N-16 (Figure ), following the same numbering convention used in the literature . This arrangement theoretically results in 64 stereoisomers or 32 enantiomeric pairs for the matrine-type alkaloids, as originally proposed by Ibragimov and co-workers . Thus far, nine stereoisomers in the matrine family have been reported (assignments of the C stereogenic centers are given in parentheses): trans -matrine ( SSSR ), , cis -matrine ( RRRS ), allomatrine ( SRSR ), sophoriridine ( SRRS ), isomatrine ( RRRR ), isosophoridine ( SSRS ), tetrahydroneosophoramine ( SRRR ), trans -neomatrine ( SSRR ), and cis -neomatrine ( SSRR ) .…”

“…Some confusion exists about the chirality labeling of the matrine compounds, especially at C-7. This issue was previously addressed by Ibragimov and co-workers . However, in a number of subsequent publications, the matrine configuration was cited or assigned as SSRR , such as in references and .…”

“…16 This arrangement theoretically results in 64 stereoisomers or 32 enantiomeric pairs for the matrine-type alkaloids, as originally proposed by Ibragimov and co-workers. 28 Thus far, nine stereoisomers in the matrine family have been reported (assignments of the C stereogenic centers are given in parentheses): trans-matrine (SSSR), 15,16 cis-matrine (RRRS), 29 allomatrine (SRSR), 30 sophoriridine (SRRS), 18 isomatrine (RRRR), 31 isosophoridine (SSRS), 32 tetrahydroneosophoramine (SRRR), 33 trans-neomatrine (SSRR), and cis-neomatrine (SSRR). 34 Some confusion exists about the chirality labeling of the matrine compounds, especially at C-7.…”

“…This issue was previously addressed by Ibragimov and co-workers. 28 However, in a number of subsequent publications, the matrine configuration was cited or assigned as SSRR, such as in references 35 and 36. A closer examination of the reported crystal structures led to the conclusion that the reported transneomatrine and cis-neomatrine in the 2003 X-ray crystallographic study 34 have the same absolute configuration at the four stereogenic carbon atoms as the reported trans-matrine.…”

Molecular Rotation Spectrum of Tetracyclic Quinolizidines: Observation of trans-Matrine and the Elusive cis-Matrine

“…20,21 However, some specific issues and the absolute configuration of several derivatives are still debatable. Concerning matrine stereochemistry, reviews by Ibragimov et al 22 based on the independent crystal diffraction observation of two different species denoted (C/D) trans-matrine 23 and cis-matrine 24 suggested that the two nitrogen atoms (N1 and N16)…”