Polyamines alkaloids

Werner C et ai, Degradation of the polyamine alkaloid aphelandrine by endophytic fungi isolated irom Aphelandra tetragona, FEMS Microbiol Lett 155 147— 153, 1997. 

MacrocycBc lactams. Two key steps in a synthesis of the polyamine alkaloid dihydroperiphylline (4) involve ring expansion of the cyclic imino ether 1 by reaction with the /3-lactam 2 to form 3. Sodium cyanoborohydride in acetic acid reduces 3 in high yield to 4, probably by way of intermediates a and b.2... 

A stereoselective Michael addition was utilized in a synthesis of the macrocyclic polyamine alkaloid lunarine. The key intermediate was generated as shown below <02JCS(P1)1115>. 

Finally there is a reaction of a N-substituted /3-lactam which had been used several times in the syntheses of natural occurring polyamine alkaloids [70] the /3-lactam VI/46 reacts on heating with 2-methoxypyrroline VI/56 [71] to form... 

The reduction of substituted 4-hydroxy-5,6-dihydropyrimidins such as VIII/ 114 is a reaction used several times as key step in the syntheses of polyamine alkaloids, Scheme VIII/21. In the presence of NaCNBH3/AcOH at 50°, ring enlarged azalactams of type VIII/115 are obtained in yields of about 90 %. Aza-lactams, prepared by this method, are nine- [65], thirteen- [66], and seventeen-membered [67] [68] [69]. 

This reaction was applied to the synthesis of the macrocyclic polyamine alkaloid celacinnine [65] a key step of this synthesis was the conversion of the bicyclic VIII/123 to nine-membered VIII/124, see Scheme VIII/23. 

PUTRESCINE, SPERMIDINE, SPERMINE, AND RELATED POLYAMINE ALKALOIDS... 

V. Catalog of Naturally Occurring Diamine and Polyamine Alkaloids. 150... 

In contrast to the polycyclic indole, isoquinoline, or terpene alkaloids, the di- and polyamine alkaloids seem to be of much simpler construction. This first impression is misleading. Special structural features render this group of alkaloids even more difficult to handle than the above-mentioned ones. It should be noted that the structures of several polyamine alkaloids have had to be revised. Because of this, two main factors should be mentioned. (1) The alkaloids sometimes occur as mixtures that are very difficult to separate, and (2) the results from spectral or chemical analyses are equivocal (cf. references on structural elucidation in Section V). This group of alkaloids was the subject of several review papers (26-28) and especially covering the subject of synthesis (29-32). Some general aspects of the difficulties associated with the isolation and structure elucidation of the polyamine alkaloids are discussed. 

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