Occurrence and Structure Elucidation

Since the previous reviews on the pavine group in Vol. 4, 10, 12, and 17 of this treatise, which cover references prior to 1976, five new alkaloids of the pavine series have been discovered. These alkaloids are (—)-2,3-methylene-dioxy-4,8,9-trimethoxypavinane (3), thalipoline, (—)-caryachine Af-metho salt (16), (-)-eschscholtzidine Af-metho salt (17), and (-)-eschscholtzine A -oxide (20a). 

A tertiary base isolated from Thalictrum strictum was assigned a pavine structure based on the spectral data (27). Three methoxyl and one methylenedioxy functions were detected with the aid of mass spectroscopy. Structure 3 was proposed as the most probable representation for this new pavine alkaloid, which indeed is the first example of a pentasubstituted pavine base. However, when the reported aromatic proton chemical shifts (8 6.23, 6.36, and 6.54) were evaluated in the light of empirical rules about the H-NMR absorptions of pavine bases (Section V,B), and it seemed possible that the two upfield absorptions belong to H-4 and H-10 rather than to H-1 and H-10. Therefore, alternative structure 4 cannot presently be completely excluded from consideration. 

A recent addition to the pavine series may be thalipoline, C has been isolated from Thalictrum minus 28). The pavine framework was deduced from spectral data which, however, were not described. 

The new quaternary pavine base (-)-caryachine A-metho salt was isolated from Cryptocarya chinensis (29), previously shown to yield both the levorotato-ry and racemic forms of caryachine (7) (30,31). The structure 16 was derived 

The structure proof of the second new quaternary base, (—)-eschscholtzidine Al-metho salt (17), isolated as its chloride from the fruits of Thalictrum revo-lutum, was provided by spectral analyses and direct comparison of the compound with the N-metho salt prepared from authentic (—)-eschscholtzidine (8), also present in the plant (32). 

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