Homalium Homaline

A (-)-homaline synthesis, which is adaptable for the synthesis of the natural unsymmetrical Homalium alkaloids, is given in Scheme VI/11 [40] [41]. The eight-membered diaza part, VI/52, was synthesized by a transamidation reaction. It was possible to prepare homaline (VI/50) and the three other minor bases, hopromine, hopromalinol, and hoprominol, by combination of different eight-membered ring building blocks. As shown in Scheme VI/11, homaline (VI/50) was synthesized in 36% yield. 

Homaline (194) is the main alkaloid of the leaves of Homalium pronyense (134-137). The bases hopromine (195), hoprominol (196), and hoproma-linol (197) have been found as minor alkaloids in the same plant (136). Homaline is composed of two cinnamic acid units and spermine. 

Details concerning the structural elucidation of homaline (57) and the related alkaloids hopromine, hoprominol, and hopromalinol, isolated from Homalium pornyense, have been published. The related spermidine alkaloid periphyllene (58) has been recently isolated from the leaves of Peripterygia marginata. Its structure and absolute stereochemistry were determined by spectral and chemical-degradation studies. 

The history of the isolation and structure elucidation of the spermine alkaloids dates from 1968, when homaline was isolated from the leaf of Homalium pronyense (Flacourtiaceae). The total synthesis of this alkaloid was reported in 1982, and the chemical structure, including absolute stereochemistry, was confirmed [2]. 

An interesting and useful translactamization process involving the -lactam (114) has been incorporated into a synthesis of the 6is-eight-membered lactam homaline (115), which is found in leaves of Homalium pronyense. ... 

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