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Book Review Nucleophilic Aromatic Displacement. The Influence of the Nitro Group. (Series Organic Nitro Chemistry Series). By F. Terrier

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Natural Products. A Laboratory Guide. 2nd Edition. By R.
I k m . Academic Press, New York, 1991. XIV, 360 pp.,
hardcover $54.95. -ISBN 0-12-370551-7
Most specialist books are either cheaply produced or too
expensive or, in the worst cases, both. The one reviewed here
is not cheaply produced; it is typeset in a clear style, printed
on good paper, and solidly bound. But what purpose does it
serve? More on this later.
The main content of the 17 chapters (about 350 pages altogether) consists of descriptions of 33 isolations of natural
products, of which 26 are from the plant kingdom, five from
the animal kingdom, and two others. In addition 15 conversion o r breakdown reactions and five total syntheses are
described. Also included are experimental data on 24 chromatographic separations and six other laboratory processes
(color reactions, formation of inclusion complexes, separation of racemates, etc.).
The contents are arranged under four main compound
classes: acetogenins. carbohydrates. isoprenoids, and nitrogen compounds. These are further subdivided; for example,
the acetogenins are divided into flavones, lipids, lignans,
quinones. and phloroglucinols. Each chapter begins with an
introduction and ends with questions and a list of recommended books. The middle part describes the individual experiments relating to the subject of the chapter.
Each introduction describes the relevant group of natural
products and explains its subdivisions. For example, steroids
are subdivided into sterins. bile acids, steroid hormones,
compounds with cardiac activity, and sapogenins. On the
whole these introductions are very detailed and well illustrated with formula diagrams, although regrettably these are
often shown as “flat” structures that are stereochemically
ambiguous. These introductions are, ofcourse, no substitute
for reading up on natural products chemistry in the relevant
textbooks, especially since they do not deal at all with the
important aspect of biosynthesis. Nevertheless, they are suitable as a first introduction o r for revision, and are presumably meant to be no more than that.
The questions are intended to serve as revision of what has
been learnt, but the chemical aspects are not adequately covered. Only rarely does one find questions about reactions or
understanding of the principles; instead the emphasis is on
names and definitions (“What is ...?” or “Describe ...”). It is
doubtful whether this style is suitable as a preparation for
examinations.
The descriptions of experiments contain many old favorites, such as Gattermann’s methods for the isolation of caffeine from tea and of heme from blood. However, some
micropreparations are also included, where the emphasis is
not so much on isolating significant quantities as on chromatographic investigations, as in the isolation of pteridines
from fruit-flies. Finally, to complete the picture, there are
some examples of conversions (e.g., cholesterol to
cholestenone. which again is old hat) and total syntheses
(e.g., mescalin---was this really necessary?). These experimental descriptions again follow a consistent pattern under
standard headings: introduction, principle of the method,
apparatus, materials. time required, and execution. The latter usually also includes information on yield, physical properties, test reactions and derivatives, spectroscopic data, and
literature references. The latter especially makes it evident
that the original edition is now 25 years old.
Some important items that have been added since the first
edition are the spectroscopic data given for most of the end
products. and details of the flash chromatography of essential oils. HPLC of carotenoids, RP-HPLC of amino acids,
HPTLC of carbohydrates. experiments on geoporphyrins,
yeast RNA, and the synthesis and breakdown of alkaloids
and steroids.
Time and again one asks “Is this necessary?” Not because
of the errors. which are very few -for example. in the formula diagrams on pages 201 and 252, in nomenclature (the
correct names are citral, not geranial, and sabinene. not
sabonene), and on page 240 where the impression is given
that strychnine can be extracted from ground-nuts. These
are pardonable sins, but more serious faults to my mind are
the unnecessarily detailed descriptions of experiments
(pp. 280f., preparation of silica gel layers on glass rods and
test-tubes for thin-layer chromatography), and sketches of apparatus whose poor print quality alone indicates that they
have probably been simply photocopied (p. 197, apparatus for
UV irradiation, and p. 200. where the flash chromatography
sketch is clearly identical to that in Still’s original publication).
Who should buy this book? Obviously it tries to achieve
too much. The whole of natural products chemistry, from
isolation and structure determination through conversions
to the total synthesis of natural products - a subject that
should certainly also include biosynthesis -cannot be compressed into 350 pages. If the subtitle “A Laboratory Guide”
is intended seriously, a good deal of this could be left out.
and perhaps also some of the old familiar stuff could be
sacrificed in favor of up-to-date procedures. At this price
students are hardly likely to buy the book, and natural products chemists will find in it little that they d o not already have
in other sources; however. interested scientists from neighboring disciplines can obtain from it a concise impression of
the variety of natural products chemistry.
Horst C. U x r
Fachbereich Organische Chemie
der Universitdt-Gesamthochschule Siegen (FRG)
Nucleophilic Aromatic Displacement. The Influence of the
Nitro Group. (Series: Organic Nitro Chemistry Series). By
E Terrier. VCH Publishers, New York/VCH Verlagsgesellschaft. Weinheim, 1991. XI, 460 pp., hardcover
DM 239.00.- ISBN 0-89573-31 2-913-527-26746-8
The attention of modern organic chemistry is directed
mostly towards control of the stereochemistry of organic
reactions, synthesis of natural products, and especially towards life processes. The chemistry of aromatic compounds,
particularly nucleophilic substitution in aromatic rings, is
presently “out of fashion” in academic research. There are
some reasons for such an attitude; nevertheless, since the
majority of products of organic chemical industry contain
aromatic carbo- or heterocyclic rings, the chemistry of arenes is still of great importance. Moreover, contrary to the
common opinion, it also offers a significant intellectual challenge and an interesting field for discoveries.
In this situation the appearance of the monograph by
Franqois Terrier is very timely and welcome. In a relatively
short volume the author discusses many important effects of
the nitro group on the reactivity of aromatic compounds
with nucleophilic agents. Thus, such problems as the kinetics
and thermodynamics of the formation of a-adducts, classical
nucleophilic aromatic substitution of leaving groups, and
many variants of nucleophilic substitution of hydrogen,
photosubstitution, etc., are thoroughly discussed, and a rich
selection of examples and references is given. As one might
expect, the author’s own preferences and interests flavor the
book to a noticeable extent. Physicochemical and mechanistic problems are discussed in more depth than practical
aspects; nevertheless, the usefulness and applicability of the
various reactions in organic synthesis is discussed at a n adequate level.
Although I am very favorably impressed by the concept of
this book and its content, I cannot refrain from some critical
remarks.
The first objection concerns terminology. Although it is
commonly accepted to use the term “complexes” for the
adducts of nucleophiles to nitroarenes, this is somewhat misleading. It implies a specific nature for the bonds formed in
the addition process. whereas they are normal a-bonds to sp3
carbon atoms. The term “a-adduct” should perhaps be used
instead of “complex”, and in Fact the former term is also
used occasionally by the author.
The second objection is more important. In the present
state of knowledge, it is evident that nucleophilic addition to
a carbon atom bonded to hydrogen (to form a dl-adduct)
takes place more rapidly than to one with another substituent (a”-adduct formation), when these carbon atoms are
in equally activated positions of the aromatic ring. This fact
is well presented in the book, and also in the author’s own
original papers and earlier reviews. From this one can draw
the general conclusion that nucleophilic substitution of a
leaving group in the nitroaromatic ring is usually preceded
by fast and reversible formation of the isomeric aH-adducts.
The author justifiably claims that n-complexes are formed in
the course of the S,Ar reaction, but does not mention the
more important pre-equilibrium of the formation of aH-adducts. Such a conclusion would undoubtedly stimulate the
search for new reactions, and would give this very interesting
book an additional value.
In a relatively concise book such as this, it is necessary to
select material, and thus some omissions are unavoidable.
However, I think that the important, although not very general, method of converting cr”-adducts into nitroso compounds should be mentioned as another variant of the nucleophilic substitution of hydrogen.
The general appearance of the book is pleasing, and the
high quality of typography and artwork makes reading it not
only an interesting, but also an enjoyable excursion into the
chemistry of nitroarenes.
There are very few typographical errors; for example, in
structure 10 (p. 162), in the side chain NO, should instead be
Me; on page 179, second line from the bottom, 5 % should
instead be 50%; on page 163, “dimethylation” (with HMPA) should read dimethylamination. The most serious error
can be seen on the back cover!: nrucleophilic substitution.
In general. this is a very valuable, interesting, and important book, and I strongly recommend it for all libraries of
academic and industrial chemical research laboratories. In
spite of the relatively high price, it will undoubtedly also be
purchased by many individual chemists. I certainly hope that
it will promote a greater interest in the fascinating chemistry
of nitroarenes.
Mieczyslaw Mgkoszu
Institute of Organic Chemistry
Polish Academy of Sciences
Warsaw (Poland)
Microbial Degradation of Natural Products. Edited by G.
Winkclmunn. VCH Verlagsgesellschaft, Weinheim/VCH
Publishers, New York, 1992. XII, 420 pp., hardcover
DM 248.00. -ISBN 3-527-28354-4
Molds and bacteria play a central role in the mineralization of all organic compounds. This book presents an
overview of microorganisms and their enzymes that are involved in the degradation of natural products. The importance of such enzymes extends far beyond degradation in the
narrower sense. They are involved in many biotechnological
processes, and are also present as supplements in various
products. Interest in natural products as renewable raw materials has increased in recent years. In Germany. for example, research on renewable raw materials has been supported by grants of about DM 50 million from the Federal
Ministry for Research and Technology alone. Therefore the
book fills a gap and is likely to be welcomed with considerable interest. N o survey of the degradation of natural products has previously been available in this form.
The editor, G. Winkelmann, has succeeded in recruiting a
team of expert authors from universities and industry. In
twelve chapters they report on the breakdown of starch,
pectin, cellulose, hemicellulose, lignin, proteins. nucleic
acids, and arenes. In nature these substrates undergo degradation by a wide variety of microorganisms, of which molds
play a central role. These organisms synthesize a great variety of amylases, glucoamylases, pectinases, and other enzymes. The current state of knowledge on the microorganisms and enzymes that take part in degradation is brought
together here. both in the text and in the numerous tables.
The chapters have a clear arrangement of subject matter, and
for each substrate there are sections on the physiology and
genetics of the microorganisms, and on the properties of the
enzymes and methods for their purification and assay. There
are also applications-related sections explaining the importance of the enzymes in biotechnology. Enzymes such as
amylases, glucose-isomerase, and proteases, which are manufactured on a large scale and are used in the saccharification
of starch, in the food industry, and in detergents are described, but the spectrum of applications is much broader.
ranging from medicine (collagenases) through fine chemicals
manufacture (thermolysin, lipases) to molecular biology (nucleases). Whereas it is not yet clear how or whether ligninperoxidases will be adopted in biotechnology, the use of
P-450 enzymes for selective biotransformations is continually being extended to new processes. Everyone interested in
such enzymes will find in this book a wealth of possible
organisms for producing them. However, whether or not a
particular one is actually obtainable is another question,
since many organisms have not been deposited in the available collections, and some of those mentioned in publications are not even accessible through the groups reporting
them.
Most of the enzymes involved in the degradation of natural products are exoenzymes, and their synthesis and secretion is therefore reviewed in the first chapter. Two other
chapters of special importance are those on arenes, which
occur in nature during the breakdown of lignin, and are also
present in amino-acids, lignin precursors, antibiotics,
flavonoids, phytoalexins, and melanins. One of these chapters is devoted to metabohzation in molds, and the other to
anaerobic breakdown of arenes. As well as being potentially
useful for the detoxification of water and soil, these reactions
also offer possibilities for manufacturing fine chemicals by
biotransformations that are environmentally friendly and
selective.
The book gives the reader an insight into the gaps in
present knowledge and the directions of future research. For
example, we d o not yet have a complete picture of anaerobic
degradation. Progress is hampered especially by the slow
growth rate of the microorganisms concerned and by the
small cell mass per unit volume of the fermentation medium.
An important advance in the understanding of lignin break-
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