Isopelletierine synthesis

Pelletierine and associated bases, pharmacological action, 62, 108 isoPelletierine, 55, 57, 58 pserwfoPelletierine, 55, 58 constitution, 59 synthesis, 61 Pellitorine, 2... 

In the six-membered series the alkaloids of Punica gr ana turn, isopelletier-ine and methylisopelletierine, have been obtained by treatment of enamines with acetoacetic acid. Isopelletierine (194, R = H) was prepared also by Schopf et al. from d -piperideine (309-311). The reversibility of aldol dimerization (124,131) of enamines has been established by the synthesis of methylisopelletierine (194, R = Me) from dimethyltetrahydroanabasine, accomplished by Lukes and Kovaf (101) (Scheme 19). 

Two new approaches to the synthesis of deoxynupharidine (14) and its C-l and C-7 epimers were reported. Arata et al. (67) made use of the Mannich reaction of a suitable derivative of isopelletierine and 3-furylaldehyde ( )-7-epideoxy-nupharidine (15) and ( )-l-epideoxynupharidine (8) were proved to be the main products of the reaction. The synthetic route is shown in Scheme 11. Intramolecular Diels-Alder condensation of 1-Azadienes was shown (68) to be a stereoselective route to the total synthesis of (-)-deoxynupharidine (14). The key steps are shown in Scheme 12 from synthon A in four steps alkaloid 14 was obtained. 

The continuing interest in the synthesis of macrocylic alkaloids has been directed this year to the preparation of the cw-quinolizidine group. It is apparent from the work of Hanaoka et al.29 that alkaline conditions for the Mannich condensation of isopelletierine (41) with aryl aldehydes, cf. (39), favour the formation of cis-quinolizidinones. The synthesis of the biphenyl ether alkaloid vertaline (48) was carried out in this way (Vol. 5), and has now been described in full.30... 

There is still considerable activity in the synthesis of Lythraceae alkaloids, although no new methods have emerged this year. Details have appeared of two independent syntheses of the biphenyl ether alkaloid decaline. - Arata s approach to the synthesis of decaline (35) cf. Vol. 5) has been applied to lagarine (36), using a benzyl group to protect the phenolic hydroxyl substituent. 4-Arylquinolizid-2-ones, cf. (34), are important synthetic intermediates, and their synthesis from isopelletierine and a variety of 2-bromobenzaldehyde derivatives has been studied. ... 

Five alkaloids have been reported as occurring in the bark of the pomegranate tree. Of these, isopelletierine, methylisopelletierine, and pseudopelletierine have been assigned satisfactory structures which have been confirmed by synthesis. The other two are pelletierine and methylpelletierine, and as already reported in Volume I, the occurrence of the latter is uncertain. Pelletierine was assigned the structure of /3-(2-piperidyl) propanal (4). Numerous attempts to synthesize a compound of this structure have failed (5-11). Although it is possible to isolate a derivative of the aldehyde, /3-(2-piperidyl) propanal itself could not be obtained. This long series of failures has raised doubts as to the existence of pelletierine or, at least, as to the correctness of its assigned structure. 

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