Psychotrine structure

In the early work (93) summarized in Chapter 3 of Volume XIII (3), two alternative structures 8 and 93 were considered for (+)-demethylpsycho-trine on the basis of its conversion to O-methylpsychotrine (7) and its formation from psychotrine (6) by acid hydrolysis and from the mass spectral evidence. The structure of (-l-)-demethylpsychotrine has now been established as 8 as a result of the syntheses of ( )-9-demethylpsychotrine (8), ( )-10-demethylpsychotrine (93), and (+)-9-demethylpsychotrine (8) by Fujii et al. (94,95). The syntheses of ( )-8 and ( )-93 (94) consisted of initial... 

Fig. (2). The structures of emetine (1), cephaeline (2), psychotrine (3), O-methylpsychotrine (4), emetamine (5), protoemetine (6)...

On the basis of and NMR spectral data, McLaughlin s group (66) has confirmed that (+)-psychotrine (3), newly isolated from the sap of P. speciosus (Jacq.) K. Schum. (Rubiaceae), has the genuine 3,4-dihydroiso-quinoline structure (the endocyclic double bond structure) as in the case (1,102) of O-methylpsychotrine (4). The same conclusion had already been reached by Fujii s group (S5) as a result of their NMR study of 3. 

A full account was also given (53) of their preliminary work (1,81, 82) on the racemic and chiral syntheses and structure establishment of alangicine (25). The NMR spectra of ( )-24 (103) and ( )-25 (53) confirmed the correctness of the endocyclic double bond structure in the dihydroisoquinoline moiety of the two Alangium alkaloids, (-I- )-9-demethyl-psychotrine (24) and (-l-)-alangicine (25). 

Two new alkaloids have been isolated from the root hark of this plant alangicine, C28H36O5N2 (mp 148° [a]p +641°), was shown to have structure V as the result of exhaustive spectral data and desmethyl-psychotrine, C27H34O4N2 (mp 168° [a]p +67.9°) which was obtainable... 

It can therefore be concluded that the structures of emetine, of psychotrine, and of 0-methylpsychotrine have been entirely determined. There remains some question as to the exact location of the double bonds in rubremetine and more serious doubt as to the structure of emetamine. ... 

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