FLAVOUR AND FRAGRANCE JOURNAL, VOL. 8, 123-125 (1993)

Book Reviews

CHIRALITY IN INDUSTRY: THE COMMERCIAL MANUFACTURE AND APPLICATIONS OF OPTICALLY ACTIVE COMPOUNDS, edited by A. N. Collins, G. N. Sheldrake and J. Crosby, John Wiley, Chichester, 1992. No. of pages: xvi + 409, price f65.00, $108.00. ISBN 0-471-93595-6.

Readers of this Journal will know the importance of chirality and will know that there are many examples of enantiomers with different biological properties. To quote examples given on page 3 of this book: the bitter taste of (S)-asparagine and the sweet taste of (R)- asparagine, the caraway flavour of (S)-carvone and the spearmint flavour of the (R)-enantiomer. Other ex- amples given here refer to antibiotics, drugs, herbicides and fungicides, and the commercial manufacture of these optically active compounds is probably more important to industry than the synthesis of flavours and fragrances. The book is an extension of a review written by J. Crosby and first published in Tefruhedron, 47, 4789 (1991), which is reprinted here as Chapter 1. Thereafter, the nineteen chapters are grouped under non-biological resolutions (3), biological methods (lo), asymmetric synthesis by chemical means (4) and im- mobilization techniques and membrane bioreactors (2) and are the work of 38 contributors. The chiral pool refers to relatively inexpensive, readily available, opti- cally active, natural products which can be used as starting material for further syntheses. From the terpene field (+)-limonene, (-)-menthol, (-)-carvone, (+)- camphor, (+)-3-carene, (-)-P-pinene, (+)-a-pinene and (-)-a-phellandrene are mentioned. Camphor derivatives, especially the 2-sultam, being crystalline, are more easily purified. World demand for (-)- menthol probably exceeds its supply from natural sources and this has prompted synthetic and semi- synthetic routes to this mint flavour, the former from

rn-cresol, the latter from either (-)-a-phellandrene or (+)-3-carene, as described in Chapter 1. In Chapter 16 the Takasago route to (-)-menthol is described by Akutagawa. Here, a chiral rhodium phosphine catalyst (Rh-BINAP) is used to isomerize geranyl and neryl- diethylamines, obtained from isoprene or myrcene, to give an optically active enamine which can be processed further into (-)-menthol, (+)- and (-)-citronello1 or (-)-7-hydroxycitronellol. In the following chapter Akutagawa reviews asymmetric hydrogenation with Rh-BINAP catalysts.

Many of the chapters are concerned with the produc- tion of optically pure natural or unnatural a-amino acids and their peptides. The production of mono- sodium L-glutamate as a flavour enhancer has been carried out in Japan since the beginning of the century and the more recent Ajinomoto process is describcd in Chapter 1. Synthetic peptides, such as aspartame and alitame, have found wide acceptance as synthetic sweeteners in food. Oyama reviews the industrial pro- duction of aspartame in Chapter 11. In the Tosoh pro- cess, benzyloxycarbonyl-L-aspartic acid is condensed with L-phenylalanine methyl ester using the enzyme thermolysin to produce up to 1000 tonnes of aspartame.

Other chapters in the book, dealing with optically active epoxides, phospholipids, P-hydroxycarboxylic acids, P-lactones, naproxen and pyrethroid insecticides, probably have less relevance for flavour chemists, who will no doubt still find much to interest them. This book will be welcomed by anyone who has to produce more than a few grams of an optically active com- pound.

ROGER STEVENS Threlkeld

NATURAL AND SYNTHETIC SWEET SUBSTANCES, A. KrutoSikova and M. Uher, first English edition, published jointly by Ellis Horwood, Chichester and VEDA, 1992. No. of pages: 223, price f45.00. ISBN 0- 13-61 2805-X; 80-224-0244-3 (VEDA).

The publication of this English edition, translated from the Czech by J. Hudec, of a comprehensive review of sweeteners, both naturally occurring and

synthetic, will be welcomed by those specialists in fields as diverse as food technology, dietetics, endocrinology, physiology, dentistry and general medicine to whom the original is not readily available or understandable. It is to the organic chemist, though, that the book will be of most value-not surprisingly, since the authors’ expertise is in that discipline.

The book is divided into four chapters, each with its own bibliography at the end of the chapter, a system

0 1993 by John Wiley & Sons, Ltd.