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Handbook of Chemical Glycosylation. Advances in Stereoselectivity and Therapeutic Relevance. Edited by AlexeiV. Demchenko

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Handbook of Chemical
Advances in Stereoselectivity and
Therapeutic Relevance. Edited by
Alexei V. Demchenko. Wiley-VCH,
Weinheim 2007.
502 pp., hardcover
E 159.00.—ISBN
In spite of the fact that achievements in
carbohydrate chemistry were awarded a
second Nobel Prize in Chemistry as long
ago as 1902, this branch of organic
chemistry has to this day lost none of
its fascination. What began more than
100 years ago with the elucidation of the
structures of these sticky compounds—
today every student knows of Fischer%s
brilliant logical deduction of the glucose
structure—and with simple glycosylation methods (such as the Fischer–Helferich or the Koenigs–Knorr methods)
has, after a long period of hibernation,
developed into an arsenal of highly
sophisticated chemical methods, which
enable the carbohydrate chemist to
selectively build most of the possible
glycosidic bonds. Since nature has created an unbelievable variety of carbohydrates, especially those of bacterial
origin, and we can at least partially
understand the biological significance of
many of their structures today, it is very
necessary to have a specialized chemical
toolkit to build any and all of those
In his newly published book, Alexei
Demchenko has produced an excellent
compilation of chemical glycosylation
methods. 15 separate essays by
Angew. Chem. Int. Ed. 2008, 47, 5281 – 5282
renowned carbohydrate chemists have
been merged into five long chapters. In
his short introduction (the book%s first
chapter) the editor elaborates on general aspects of the glycosylation reaction. The novice is thus introduced to
the basics and to the problems of
carbohydrate chemistry; the importance
of protecting groups and leaving groups
as well as that of solvent effects and
promoters is explained, and problematic
glycosylations such as sialylations and bmannosylations are also touched upon.
The second chapter deals in detail
with the use of anomeric glycosyl halides. Besides the older studies on the
Koenigs–Knorr glycosylation, it is especially the glycosyl iodides and the thermally stable glycosyl fluorides that have
received a lot of attention within the last
25 years. The significance of oxygensubstituted glycosyl donors is dealt with
in Chapter 3, the most comprehensive of
this monograph. Besides hemiacetals
and alkyl and silyl glycosides, attention
is, of course, focused on the trichloroacetimidates, phosphites, and phosphates. Schmidt—the father of the
describes in detail the success story of
this method. The story began in 1980,
and the trichloroacetimidates are still
the most widely used glycosyl donors
today. The highly complex structures
described in this chapter reveal the great
potential of these donors, even for use in
automatic synthesis. It remains to be
seen whether the N-phenyltrifluoroacetimidates will take their place in the
future. The topic of Hashimoto%s subchapter is glycosylation as it occurs in
nature, that is to say, using phosphates as
the leaving group. The donor can be
prepared easily by using glycals or
orthoesters, which is why the method
has lately gained great practical significance. Sulfur- and selenium-derived
donors are the topic of Chapter 4.
Boons reports on fascinating chemoselective glycosylations and one-pot
syntheses based on relatively stable
thioglycosides. The remaining parts of
this chapter (Crich and Field) cover
sulfoxides, thioimidates, xanthates, and
The final chapter, entitled “Other
Methods”, contains a veritable potpourri of glycosylation methods. Here
Fraser-Reid deals with the important
orthoesters, and impressively demonstrates their synthetic utility. Danishefsky%s glycal methodology and Ito%s successes with intramolecular b-mannosylations are outlined. Beyond that, exotic
donors such as diazirines, telluroglycosides, and tetrazoles are mentioned.
References to palladium-catalyzed glycosylations and to the use of [4þ2]
cycloadditions for forming glycosidic
bonds hint at future possibilities that
may be limitless.
I read this book with great pleasure,
and above all learned a great deal about
the special glycosylation methodologies
(especially about those of a more academic nature described in the fifth
chapter). Particularly helpful for practical use are the examples of protocols for
the synthesis and/or conversion of the
respective donors that are given at the
end of each chapter.
However, I cannot understand why,
whereas some of the authors consistently number the compounds (thus
adding greatly to the clarity of the
text), others neglect this practice completely. Another annoyance (of a more
visual nature) that this book shares with
many other multi-author collections is
the inconsistent layout of structural
formulas: their perpetually varying
sizes, fonts, styles, and stereochemical
or non-stereochemical depictions. Editors and publishing houses should
ensure that, with the aid of templates,
a uniform visual layout is achieved.
To conclude, I recommend this monograph to all those who deal with
carbohydrate chemistry or wish to do
so. To the experienced carbohydrate
chemist it serves as a work of reference
(containing more than 2000 literature
citations), and to the novice it serves to
expand his or her knowledge of glycosylation methods. However, a reader
entirely unversed in the subject matter
might find it difficult to differentiate
between methods according to their
relevance or otherwise, and their greater
or lesser degree of efficacy. Still, I hope
that this book will generally be of help in
eliminating the reservations that many
organic chemists have on the subject of
carbohydrates. One question, however,
does remain, especially if we consider
the rapid and highly selective advances
in the synthesis of complex carbohydrates in future: Will one widely appli-
- 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
cable methodology for the chemical
construction of oligosaccharides eventually prevail, as we have seen occurring
in the realm of automatic peptide syntheses?
Daniel B. Werz
Institut f3r Organische und
Biomolekulare Chemie
Universit7t G8ttingen (Germany)
DOI: 10.1002/anie.200785610
Dynamic Stereochemistry of
Chiral Compounds
Principles and
Applications. By
Christian Wolf.
Royal Society of
Chemistry, Cambridge 2007.
512 pp., hardcover
£ 49.95.—ISBN
Chirality is a key feature of natural
compounds and plays an essential role in
amino acids (and hence in peptides and
proteins), sugars, and numerous bioactive substances. Consequently, organic
chemists have developed a plethora of
methods for the synthesis of chiral
compounds starting from the chiral
pool, by separation of racemic mixtures,
or by performing asymmetric syntheses
from achiral precursors. For the latter, a
broad variety of concepts have been
developed, with homogeneous and heterogeneous catalysis as the most important current methods, but biocatalysis is
also used to obtain optically pure chemicals. Furthermore, a wide range of
analytical tools for the determination
of the optical purity and absolute con-
figurations of chiral compounds have
been established in the past. More
recently, stereochemistry has also
turned out to play an important role in
nanomaterials and in the development
of molecular chiral devices.
The book by Christian Wolf is
organized in three parts and contains
nine chapters. The first chapter gives an
introduction to the topic. Chapter 2
describes the basic principles, terminology, and nomenclature of stereochemistry. This part is very useful, as it provides
practical guidelines, not only to understand the rest of the book but also to
determine, for example, the R or S
configuration of complex or rather
unusual compounds. Racemization,
enantiomerization, and conformational
isomers are covered in the third chapter,
together with mathematical treatments
and mechanistic insights. The next chapter is devoted to analytical methods,
with special emphasis on chirooptical
methods, NMR spectroscopy, dynamic
chromatography, and stopped-flow analysis. Thanks to Wolf%s recommendation,
one can now freely use the term “chiral
chromatography” to describe GC or
HPLC methods using chiral phases.
The second part of the book focuses
on asymmetric synthesis as the most
important synthetic method to create
chiral compounds. First, the principles of
asymmetric synthesis are introduced,
and that is followed by numerous practical examples using a broad range of
catalysts, both chiral and nonchiral. In
the following chapter, kinetic resolution,
dynamic kinetic resolution, and related
strategies are treated in depth. Many
examples are also explained in detail
from a mechanistic standpoint, so that
the reader can get a clear understanding
of the basic principles behind a given
stereoselective reaction.
The third and last part of the book
deals with a rather new and—in my
view—somewhat esoteric research field:
- 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
stereodynamic devices and manipulation of molecular motion, where topological chirality plays a crucial role in
the design of molecular propellers, bevel
gears, brakes, switches, motors, etc. This
section also includes the synthesis, chirality, and stereodynamics of catenanes,
rotaxanes, and related compounds. The
book ends with an extensive and very
useful glossary of stereochemical definitions and terms, followed by an index.
Biocatalytic methods are adequately
covered in the chapter about (dynamic)
kinetic resolution. However, I was disappointed to find that the use of
enzymes in asymmetric synthesis,
where they indeed play an important
role and are applied in many industrial
processes, is not covered. Examples such
as the use of ketoreductases to prepare
chiral alcohols, and of hydroxynitrile
lyases or aldolases to perform CC
coupling reactions, should at least have
been mentioned briefly.
The only error I found was in the
equation for measuring optical rotation
by polarimetry, where the concentration
c of a compound was given in g/ml,
whereas it should read g/100 ml.
Overall, I was highly impressed by
the excellent scientific level of the book,
the language style, which made it a
pleasure to read it (if reading a chemistry book can be pleasurable at all), and
especially the care taken to illustrate the
examples with numerous (often highly
complicated) chemical structures, reaction schemes, and mechanisms.
Without any doubt, I strongly recommend this book to advanced students
and experienced chemists, as it is a very
rich source of information on all aspects
of stereochemistry.
Uwe Bornscheuer
Institut f3r Biochemie
Universit7t Greifswald (Germany)
Angew. Chem. Int. Ed. 2008, 47, 5281 – 5282
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stereoselective, advanced, chemical, therapeutic, handbook, glycosylation, alexeiv, edited, relevance, demchenko
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