418 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS product and the presence of a hemilactal system- entirely unique in natural and synthetic products. Shemyakin and Antonov (Moscow Natural Products Institute) present a most useful review of intramolecular enzymic transpeptidation. They cite examples of formation of N-acyl amides important in metabolism and biosynthesis and of the determination of structures resulting from incor- poration of hydroxyl or aminoacyl groups, using UV, IR, NMR and mass spectroscopy. They discuss the criticality of ring size in the expansion of N-acyl cyclic lactams to form peptide lactones and outline a number of biogenetic pathways for peptide antibiotics such considerations may also be applied to proteins and hormones. K. Biemann (M.I.T.) describes in considerable detail the utility of high resolution mass spectroscopy in the examination of natural products, particularly for the very accurate determination of molecular weights and the study of fragmentation mechanisms leading to structural assignments. There are two distinct systems: Both employ preliminary electrostatic focussing in addition to the conventional electromagnetic stage. Beynon employs a single focus low resolution scan followed by double focussing to examine peaks of special interest. Biemann considers this time- consuming for general use he employs a computer to analyse a photo- graphic record of a complete HR mass spectrum, which assigns mass with a precision of one part in 100,000 by comparison with an internal standard, and is then able to deduce the correct elemental composition of fragments that are superposed in conventional low resolution instruments. Examples from steroid and alkaloid fields, using both techniques, are discussed in detail one at present totally unknown structure is included to demonstrate the 'potential of his version. Prof. V. Prelog (ETH, Zurich) refers to his earlier examination of micro- biological reduction of alicyclic ketones (especially d ecalin-l,4-diones), frequently with the production of a preferred enantiomer, which has led naturally into an investigation of product stereospecificity in enzyme reactions. Whilst the enzyme infra-structure plays an important role, such interaction cannot be the sole factor. The development of Prelog's diamond lattice theory for the spatial relation of the reactive groups is therefore particularly significant. Prof. Stork (Columbia University, New York) gives a detailed account of annelation reactions that he has found especially useful in the total synthesis of natural alicyclic systems. Having shown his versatility in the construction of steroid rings B and A, from a basic decalenone starting

BOOK REVIEWS 419 point, he proceeds to a stimulating description of the solution of structural and stereochemical problems in the manufacture of a tricyclic quinolone which should yield members of the aspidospermine alkaloid family. Prof. Th. Wieland (University of Frankfurt/Main) contributes a con- densed but most readable account of the elucidation of the structure of a group of bicyclic peptide toxins extracted from a letlml species of mush- room found in Central Europe. He first reviews his earlier work on tl•e more rapidly toxic phalloidine heptapeptide congeners and then reports his most recent studies establishing the structure of the four related amanitine toxins the members of latter group differ in being octapeptides with a 6-hydroxyl in the interesting 2(S)-cysteinyl-tryptophan moiety. The progress of mass spectroscopy is survey by Carl Djerassi (Stanford University, California). He briefly comments on electronic control in fragmentation mechanisms and then develops his main theme -the impor- tance of isotopic labelling in mass spectroscopic studies. Instances are cited revealing the composite nature of cleavage products having the same empirical composition, i.e. which would not be distinguished even by high resolution mass spectroscopy. Details are given of his extensive experience with deuterium labelling whereby hydrogen transfer rearrangements may be detected. Finally, Prof. J. Monteath Robinson (Glasgow University) presents a concise, polished review of the present status of X-ray crystallograpl•ic solution of natural product structures. To illustrate tl•e use of his l•eavy atom labelling tecl•nique, he cites derivatives of natural products witl• both favourable and unfavourable phase situations and then gives examples employing isomorphous replacement or solrated crystals. He mentions a number of terpenoid bitter principles elucidated during a most fruitful collaboration with the natural product schools in Glasgow of Barton and, currently, Raphael. Altogether, this book contains a fascinating collection of lectures, admirably balanced despite the contemporary preoccupation with physical techniques. It is a worthy successor to the two previous volumes all three are essential reading for any chemist having an interest in natural products and are profitable study for those in less specialised fields. G. F. PHILLIPS.