Recent developments in the chemistry of natural phenolic compounds

BOOK REVIEW Recent Developmentainthe CI2mhby of Natard Phenok Compounds;Ed. by W. D. OI+MS. Pp. 237. Pergamon Press Ltd., 1961. 70s. A SWIESof papers read at a meeting arranged by the “Plant Phenolics Croup” in 1960 have been collected in this valuable volume. They cover important recent advances in the Chemistry of Natural Products and deal with biogenetic, bios~~etic and synthetic problems as well as the structural election of new plant phenolics. R. W. Richards has written an excellent review on the role of acetic acid in the biosynthesis of phenolic compounds. The “acetate hypothesis” was proposed by Collie and has frequently been used by Sir Robert Robinson to explain the hydroxy~tion pattern in several phenolic natural products. It has recently been developed in considerable detaiI by Birch and now ranks as a useful theory allowing some predictions to be made; these have actually been conflrmed in several cases by structural reinvestigations and biochemical studies. W. B. Whalley’s thorough discussion of structural relations in the phenol series is very stimulating. These mainly speculative contributions which are coloured by the biogenetic optimism of the organic chemist are followed by H. Griesebach’s report on what is known to date about the biosynthesis of flavonoids, particularly the isoflavones. W. D. Ollis and I. 0. Suth~~ deal with the large number of phenolic compounds contai.ning i~p~noid components. The actual combination of the phenolic and isoprenoid moieties poses an important biochemical problem. C. H. Hassal and A. L. Scott discuss recent work on the in vitro synthesis of a series of compounds which, at least formally, appear to result from the oxidative coupling of simple phenols. The chemistry of tannins has recently undergone rapid development due to improved analytical methods and brief summari es of the work of the Sheffield school are given by R. D. Haworth and E Haslam. 0. Th, Schmidt describes the brilliant work which has been ~p~~~ in Hider on strobe tannins. The interesting story of the discovery and structural elucidation of the “bitlavonyls” is told by W. Baker and W. D. Ollis who, together with Japanese chemists, have contributed a great deal to this field. The literature on bitlavonyls is somewhat inaccessible to western chemists since many papers are in Japanese. This paper introduces a new feature in the book, that of ch~o~on~y. The biflavonyls have mainly been isolated from the leaves of gymnosperms and their occurrence appears to be limited to certain groups. The non-methylated amentoflavone has recently been found in a pteridophyte (Sergei&). Strangely enough ~no~vone has been isolated from an angiosperm (CMZUZ&U). The statement that among the angiosperms this gemts is specially closely related to the gymnosperms should perhaps be taken with a pinch of salt. A systematic search for biflavonyls in angiosperms is, however, to be recommended. The curious “‘carbon-glycosides” found in several plant families are discussed by L. H&hammer and W. Wagner. They furnish interesting biosynthetic problems. D&ding’s contribution on ‘betacyanines” such as the “nitrogenous anthoycanin”, from red beet, is very fascinating. The structure of these compounds has long remained obscure, again mainly because of isolation ~~~ti~. However, they have now been revealed as complex indole derivatives. Their occurrence in the vegetable kingdom appears to be restricted to the orders C&ales and Centrospermae (with the notable exception of 223

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BookReview

Caryophylliriae which contains normal anthocyanins). This is very interesting since botanists (e.g. Schumann, Engler) have long assumed that these orders are phylogenetically related in spite of the fact that they are, systematically, far apart. W. D. Ollis and I. 0. Sutherland &ally discuss a series of tetracene quinones of fungal origin in relation to the “acetate theory”. Reviews like the present one, written by experts engaged in active research in their particular fields, are invaluable to their colleagues and highly stimulating for the younger generation of chemists that has just started research or is preparing for scientific careers. Unfortunately, however, in many of the reviews only the very latest papers are referred to and this sometimes obscures the historical perspective. Science is not merely a collection of facts and theories. It is easy to see that phytochemistry leads directly into the domains of biochemistry and biology. The present book is written by chemists most of whom have demonstrated the wide scope of their interests. It will be interesting for future chemists to return to this book and see which of the speculations have survived the biochemical ordeal. The Plant Phenol& Group is to be congratulated on the success of its efforts. lJnivt?rsi!yofstoc&~

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