Formation of ethers of pseudobases from salts of the quaternary alkaloids sanguinarine and heleritrine

Structure of Chelerythrine Base

“…The 'H-nmr signals of 5,6-dihydro-6-deuteroxychelerythrine [2b] (pseudobase deutero analogue) were recorded as: 2.59 (N-methyl), 3.86, 3.88 (two methoxy groups), and the singlet of the H-6 proton at 5.79 ppm. These chemical shifts are in good agreement with the published nmr data of 5,6-dihydro-6methoxy(ethoxy)chelerythrine [2c,d], where the signals of the H-6 atom were near 5.60 ppm and resonances of both methoxy groups were around 3.90 ppm (1,(13)(14)(15)(16)(17). In addition to the adduct 2b, the resonances of the dimer 3 were observed in the 'H-nmr spectrum.…”

“…The singlet exhibited by H-6 at 6.60 ppm was considered a significant feature. Its very deshielded resonance differs from the corresponding H-6 signals of the chelerythrine derivatives that have been described (1,(13)(14)(15)(16)(17). Only 5,6dihydro-6-acetoxychelerythrine [2e] has been reported to display the chemical shift of the H-6 proton at 6.55 ppm (18).…”