Pavine and isopavine alkaloids

The pavine and isopavine alkaloids of the Papaveraceae have been discussed in Vols. 4, 10, 12, and 17 of this treatise (2-5), and only brief references have been made to occurrences outside this botanical family. Individual chapters have been devoted to the pavine and isopavine alkaloids in the two books by Shamma (6,7), covering developments until 1977, and also in Rodd s Chemistry of Carbon Compounds (8), published in 1978. A listing of naturally known pavines and isopavines up to 1975, with references to physical and spectral data, appeared in Kametani s Chemistry of the Isoquinoline Alkaloids 9,10). A more recent compilation by Gozler and co-workers 11) has covered references to mid-1982. Relevant literature has also been summarized regularly in Vols. I-XIII of Spe-... 

It has been emphasized that either pavines or isopavines can be obtained selectively depending on the choice of acid conditions used in the aforementioned cyclization process (777). It is also apparent that acid-catalyzed cycliza-tion at room temperature results almost solely in the production of isopavines, whereas application of heat at this stage, which promotes dehydration of the 4-hydroxy intermediate, affords a mixture of pavine and isopavine alkaloids in varying ratios (770,772). 

The absorption maximum of isopavine alkaloids appear at 290-294 nm. The shoulder at 250 nm, which is missing in the spectra of pavines, provides complementary information in distinguishing between pavine and isopavine alkaloids (7,67,69). Additionally, the Hofmann degradation products of the two nuclei have been shown to differ greatly in their UV spectral behavior (67,69,75). 

The fact that pavine and isopavine alkaloids have the same absolute configuration also suggests an alternative biosynthetic sequence where both nuclei are derived from a common 4-hydroxybenzyltetrahydroisoquinoline precursor (Scheme 35) (77,135). A dehydration reaction to afford a 1,2-dihydrobenzyliso-quinoline, followed by cyclization, would yield a pavine. Alternatively, dis-... 

The fact that the pavine and isopavine alkaloids have the same absolute configuration points to the possibility of a common biogenetic precursor such as the 4-hydroxyreticuIine (9b) (or the already mentioned 4-hydroxy-norlaudanosoline (9a)] which, depending upon the plant family or genus, can cyclize directly to an isopavine species or alternatively can undergo dehydration, double-bond isomerization, and intramolecular cyclization to a pavine analog (584) (Scheme 26). 

Scheme 26. The possible common pathway of the biosynthesis (and. the absolute configuration) of pavine and isopavine alkaloids (3, 584).

Amurmsiiw see pavine and isopavine alkaloids. Amurine see morphinan alkaloids. 

Acgemonine see pavine and isopavine alkaloids. L-Anglnbie [(5)-2-Amino-S-guanidinopentanoic acid, abbreviation Arg or R). 

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