Papaverine alkaloids conversions

Papaverine, C20H21O4N. This alkaloid, first obtained by Merck, occurs in the mixture precipitated by ammonia from the mother liquors of opium extract from which morphine and codeine have been separated in Gregory s process, and methods for its isolation from this mixture have been published by Hesse and others. The alkaloid may be purified by conversion into the acid oxalate, B. H2C2O4, m.p. 196° or 201-5-202°, which is nearly insoluble in alcohol. 

Dealkylations have been used in the regioselective conversion of methoxyaryl groups to phenols in natural products, particularly alkaloids 1471 such as papaverine (30), and in the production of mammalian metabolites by microbial biotransformation, as exemplified by the biotransformation of bisprolol (4). 

The first reported biotransformation by means of cell cultures of P. somniferum was the conversion of thebaine to codeine (453). As P. som-nifemm cell cultures only produced alkaloids derived from (5)-reticuline (e.g., sanguinarine. Fig. 9) but none of the alkaloids derived from (/ )-reticuline, Furuya et al. 461) administered (R,S)-reticuline to the cell suspension cultures. After 3 days the alkaloids were isolated. Two alkaloids derived from (5)-reticuline were identified cheilathifoline and scoulerine. A third alkaloid isolated was identified as pure (/ )-reticuline. Thebaine, morphine, and codeine were not metabolized by these cell cultures. However, the cells were capable of stereospecifically reducing codeinone to codeine. Tam et al. 462) also found the same bioconversion. Furthermore, the conversion of thebaine to neopine was reported. Codeine, neopine, papaverine, and D,L-laudanosoline were not metabolized. Enzymatic reduction of codeinone to codeine was also achieved with cell-free preparations of whole plants of both P. somniferum and P. bracteatum 464). Yeoman and co-workers 108,465) reported the use of in reticulate polyurethane immobilized P. somniferum cells for this bioconversion. 

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