Classical type phthalideisoquinolines are derived biogenetically from tetrahydroprotoberberines, and the former in turn lead to the secophthalideisoquinolines. The secophthalideisoquinolines may come in different forms including enol lactones, keto lactones, keto acids and diketo acids. The most logical biogenetic sequence appears to be classical type phthalideisoquinoline-^classical type phthalideisoquinoline .Y-metho salt->secophthalide enol lactone->secophthalide keto acid->secophthalide diketo acid. Thus if one were to start with (-)-bicuculline (1), the sequence would be 1-»( -)-bicuculline .Y-metho salt (la)->the Z enol lactone aobamidine (32)->the keto acid adlumidiceine (36)->the diketo acid bicucullinine (42) (100). A seco diketo acid may then undergo oxidative cleavage to yield the alkaloid fumariflorine (51), or one of its analogs. Alkaloids of the fumariflorine type may thus represent a final stage in the catabolism of the phthalideisoquinolines (101). It is worth noting here that the presence of classical type phthalideisoquinoline .Y-metho salts has been detected in Fumaria parviflora Lam. ( 70).An enol lactone such as aobamidine (32) may undergo photoisomerization to a mixture of Z and E isomers, and in fact the E analog of aobamidine is known as a natural product under the name adlumidiceine enol lactone (33).It has recently been shown that secophthalideisoquinoline enol lactones readily react with ammonia to form hydroxy lactams (e.g. fumschleicherine (50) ). A secophthalide hydroxy lactam can then undergo facile dehydration to an enelactam. Four enelactams have been apparently isolated from natural sources, namely, fumaramine (45), fumaridine (46), fumaramidine (48), and narceine imide (49). Since ammonium hydroxide is usually used in the course of the isolation, it seems likely that these four compounds, together with fumschleicherine (50), are artifacts of isolation. Until and unless the presence of secophthalideisoquinoline hydroxy lactams and enelactams is conclusively demonstrated in the plant extracts prior to treatment with ammonia, it can be concluded that they are artifacts and not true alkaloids (100). Nevertheless, and for the sake of completeness, the hydroxy lactam fumschleicherine (50) and the four enelactams 45, 46, 48, and 49, have been included in the present listing.The secophthalideisoquinoline keto acid nornarceine (40) may also be another artifact. It is the only known seco base which does not incorporate a complete ,. -dimethylaminoethyl side chain. It was isolated only once, and that time from opium, and it may very well have arisen from the known in vitro N-demethylation of narceine (39) in acid solution (100).All uv data are in nm with log < values between parentheses. Ir frequencies are in cm-1.The nmr chemical shift values quoted are from the first reference cited. However, in case we have found it necessary to modify the original assignment, this has been indicated by a double asterisk (**) as a superscript immediately after the reference. Whenever possible, we have ...
