Secoisoquinoline alkaloids

In recent years a number of new isoquinoline alkaloids of untypical structures, i.e., structures with open heterocyclic rings, have been isolated from natural sources. These bases were named secoisoquinoline alkaloids because they were believed to be produced in vivo from classic isoquinoline alkaloids as a result of various degradation processes causing oxidative cleavage of some bonds. 

From a historical standpoint, the first secoisoquinoline alkaloid was narceine, isolated from opium by Pelletier as early as 1832 (/). Up to 1986, over 70 secoisoquinoline alkaloids had been discovered. Most of them were found... 

When discussing seco alkaloids the question of their genesis should not be disregarded. Are they true alkaloids or artifacts of isolation It is difficult to answer this question with certainty. Some of them, e.g., secophthalide-isoquinoline ene lactams, are postulated to be formed during the extraction process however, most of them are believed to be metabolites produced naturally. This may be evidenced by the fact that some of these alkaloids retain optical activity, and in addition many of them can be synthesized in biomimetic syntheses in the laboratory. Thus, one can generalize the opinion of Shamma (10), whose significant contribution to the field of secoisoquinoline alkaloids should be acknowledged, that [a process]. .. could presumably occur in vivo at least as readily as it could in vitro. ... 

The first secoisoquinoline alkaloid discovered was the secophthalideisoquinoline, narceine (106), isolated from opium by J. Pelletier in 1832 (7). Up til now 19 natural bases belonging to this group have been isolated, and 6 others have been synthesized. Secophthalideisoquinoline alkaloids have been described in several reviews papers by Shamma et al. 2,4,5), by Santavy (7), and most recently, in 1985, by MacLean (5). 

The main mass fragmentation of secobenzylisoquinoline alkaloids involves bond cleavage between the two benzylic carbonyls. This process is evidenced by the presence of peaks representing fragment ions at m/z 151, found in spectra of all these bases and attributed to the lower portion of the molecules, and ions at m/z 220,236, and 222, found in spectra of 159,160, and 161, respectively, formed from the upper part of the compounds. Similarly, as in the mass spectra of other secoisoquinoline alkaloids incorporating the amino-ethyl substituent, the [H2C=N(CH3)2]+ ion at mjz 58 is the base peak. 

Senecio alkaloids, see Pyirolizidine alkaloids Secoisoquinoline alkaloids, 33, 231 (1988) Securinega alkaloids, 14, 425 (1973) Sinomenine, 2, 219 (1952)... 

Senecio alkaloids, see Pyrrolizidine alkaloids Secoisoquinoline alkaloids, 33, 231 (1988)... 

A comparative study was reported using 1,3-dithianes and 0-benzoylated cyanohydrins respectively for the synthesis of several analogs of secoisoquinoline alkaloids bearing a dimethylamino side chain and a benzilic or reduced benzilic groupJ ... 

---