Eucomis

A reaction which involves both ring atoms and substituent is of considerable interest because the substrate is of a naturally occurring class of compounds. 3-Arylidene-chromanones (585) or homoisoflavanones, when heated with nickel in xylene isomerize to the 3-benzylchromone (586) (74IJC281) a number of homoisoflavanones occur in the bulbs of Eucomis bicolor, for example, eucomin (585 R = OH, Ar = 4-MeOC6H4). The stereochemistry about the double bond of compound (585 R = MeO) is altered from (E) to (Z) by irradiation at 300-400 nm (8lFOR(40)l05>. 

The structure of eucosterol (17), a novel spirocyclic nortriterpenoid from Eucomis spp., has been established by X-ray analysis of the mono-p-bromobenzoate.20 The loss of a terminal methyl group is unusual. 

The full details of the structural elucidation of eucosterol (26), a novel spirocyclic norlanostene from several Eucomis species, have appeared. Two additional compounds from the same source are 16/8-hydroxyeucosterol (27) and the carboxylic acid (28). The latter was prepared from (26) by base-catalysed elimination and... 

The homoisoflavanones belong to a small family of natural products whose first member was isolated by Boehler and Tamm in 1967 from bulbs of Eucomis bicolor Bak. (9). Their discovery resulted from a systematic chemical analysis of Liliaceae for cardiac glycosides. However, unlike the botanically closely related Urginea maritima (L.) Bak. (Squill) and some species of Scilla, Ornithogalum and Dipcadi 33), Eucomis plants did not contain even traces of these compounds. 

The genus Eucomis is indigenous to southern and eastern Africa. The widespread E. autumnalis (Mill.) Chitt. (Syn. E. undulata Ait.) has been used by native medical doctors against rheumatism, veneric, mental and many other diseases. A cardiotonic action has not been observed (75). A botanical survey revising this genus had been published by Reyneke in 1972 61). 

Other metabolites like 5,7-dihydroxy-8-methoxychroman-4-one (37) and possibly a coumarin derivative (35) have also been found in the bulb wax of E. comosa. From the bulb tissue of different Eucomis spp. a series of sterol derivatives, dibenzo-a-pyrones and a dicarboxylic acid have been isolated (69, 82). 

The chemical and physical properties of the homoisoflavanones and of further metabolites isolated from Eucomis spp. have been summarized earlier by Tamm (69) and Ziegler and Tamm (82). 

Table 8, Incorporation Experiments with Eucomis bicolor...

So far reports of simple homoisoflavanones are restricted to the two genera Eucomis and Scilla, both belonging to the family Liliaceae, subfamily Scilloideae. A preliminary investigation of 28 species from 10 genera of this subfamily revealed that phenolic compounds occur quite commonly in the bulb waxes (Table 10). 

Fig. 2. Two-dimensional chromatograms of bulb wax phenolics of (A) Eucomis bicolor and (B) E. comosa (see text). The individual numbers refer to the compounds listed in...

Biosynthesis of the 3-Benzylchroman-4-one Eucomin in Eucomis bicolor. Phytochemistry 14, 983 (1975). 

Farkas, L., A. Gottsegen, M. Nogradi, and J. Strelisky Synthesis of Homo-isoflavanones-II. Constituents of Eucomis auturrmalis and E. punctata. Tetrahedron 27, 5049 (1971). 

Finckh, R. E. Isolierung und Strukturaufklttrung homoisoflavonoider Verbindungen aus Eucomis punctata L Herit. Ph. D. Thesis, Basel 1970. 

Heller, W., P. Andermatt, W. A. Schaad, and Ch. Tamm Homoisoflavanone IV. Neue Inhaltsstoffe der Eucomin-Reihe von Eucomis bicolor. Helv. Chim. Acta 59, 2048 (1976). 

Reyneke, W. F. N Monografiese Studie va die Genus Eucomis L Herit. in Suid-Afrika. M. Sc. Thesis, Pretoria 1972. 

Ziegler, R., and Ch. Tamm Isolation and Structure of Eucosterol and 16P-Hydro-xyeucosterol. Two Novel Spirocyclic Nortriterpenes and of a New 24-Nor-5a-chola-8,16-diene-23-oic Acid from Bulbs of Several Eucomis Species. Helv. Chim. Acta 59. 1997 (1976). 

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