Isoquinolinium Salts into Pseudobases

The ease of formation of pseudobases (carbinolamines) from a variety of isoquinolinium salts has been investigated. Increasing pH facilitates pseudobase formation. Nitidine forms a pseudobase more readily than berberine, while 6,7-dimethoxy-2-methylisoquinoline did not form a pseudobase even at pH 13.2 Sanguinarine and chelerythrine acetates exist in an equilibrium mix- 

(+)-Reticuline is an effective precursor for chelidonine, whereas its enantiomer is not. 

( —)-Scoulerine is well incorporated into chelidonine, but its enantiomer is ineffective. (-)-Scoulerine is also converted into sanguinarine and chelery-thrine. 

If the chiral center of (—)-scoulerine is labeled with tritium, there is complete loss of tritium as the conversion to chelidonine takes place. This result supports the intermediacy of the enamine 26. 

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