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Book Review Asymmetric SynthesisЧThe Current State of the Art Asymmetric Synthesis. Edited to James D. Morrison

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Asymmetric Synthesis-The Current State of the Art
Asymmetric synthesis was considered as an academic
curiosity until the 1950’s, when a better understanding of
reaction mechanisms and the development of conformational analysis revived interest in the field. During that period much attention was given to the interpretation and
prediction of the steric course of reactions (Cram’s rule,
Prelog’s rule, nomenclature, ...). I n these investigations the
absolute configurations of many compounds were determined. At the same time, many asymmetric reactions leading to optically active products were studied, but their preparative value remained low. The now classical book of
J . D. Morrison and H . S. Mosher “Asymmetric Organic
Reactions”“’ fully reviewed the field up to the 1970’s. In
this book there are only a few reports of asymmetric syntheses with ee’s higher than 90%. During 1970-1982 there
was a tremendous increase in the number and efficiency of
asymmetric syntheses. Many stoichiometric or catalytic
reactions which lead to chiral products with ee’s higher
than 90% became routine. Moreover, the progress of modern technology rendered the setting u p of reliable methods
(based on NMR, or HPLC) for the measurement of enantiomeric excesses possible. It was therefore very appropriate that J. D. Morrison decided upon a new venture;
namely, to edit a series of five volumes devoted to the progress of asymmetric synthesis in the seventies and early
eighties. The complete work,
Asymmetric Synthesis. Edited to James D. Morrison. Academic Press, Orlando, FL, 1983-1985.
Vol. 1 , xiv, 201 pp., bound, $ 32.00.-ISBN 0-12-507701-7.
Vol. 2 , xiv, 278 pp., bound, $ 45.00.-ISBN 0-12-507702-5.
Vol. 3, xiii, 578 pp., bound, $ 84.50.-ISBN 0-12-507703-3.
Vol. 4, xii, 380 pp., bound, $ 85.00.-ISBN 0-12-507704-1.
Vol. 5 , xiv, 391 pp., bound, $ 85.00.-ISBN 0-12-507705-X
which was written in collaboration with some 60 authors,
who are also major contributors to various aspects connected with the art of asymmetric synthesis, was published
between 1983 and late 1985.
Volume 1 begins with a short chapter written by J. D.
Morrison on the various ways to obtain optically active
compounds. This volume is indeed useful for everyone
working on optically active compounds prepared either by
resolution, asymmetric synthesis or arising from natural
products. It is exclusively devoted to the purpose of measuring enantiomeric excess (ee) by direct or indirect methods and is not primarily concerned with the measurement
of diastereomeric composition. The analytical methods
which are described cover the whole spectrum of techniques with many useful indications for the practitioner. In
Chapter 2, G . G. Lyle and R. E. Lyle present various aspects of polarimetry, including details of commercial apparatus. Determination of maximum specific rotations by
competitive reactions is then dealt with in Chapter 3 ( A . R .
Schoofs and J. P. Guette). In Chapter 4, K . K . Andersen, D.
M . Gash, and J . D . Robertson explain how isotope-dilution techniques can be used to measure ee values. Gas
chromatographic methods are presented by V. Schurig in
Chapter 5 , while W. H . Pirkle and 1. Finn discuss the separation of enantiomers by liquid chromatographic methods in Chapter 6. The volume concludes with three chapters on NMR spectroscopic methods for the analysis of en848
antiomers using chiral derivatives (S. Yamagushi, Chapter
7), chiral solvating agents ( G . R. Weisman, Chapter 8), and
chiral shift reagents ( R . R. Fraser, Chapter 9).
Subsequent volumes cover various chemical reactions in
which one or several asymmetric centers are created under
the control of either external chirality centers (in a reagent
or catalyst), or internal chirality centers (in the substrate).
The diversity of situations emphasizes the difficulty of defining the exact meaning of “Asymmetric Synthesis”,
which is the title of this work. Some reactions are clearly
oriented towards the creation of asymmetric centers and
isolation of chiral products after removal of the chiral auxiliary material. These fit the classical definition of asymmetric synthesis (Enantioselective Synthesis of Chiral
Compounds). Another group of transformations is also
discussed in the work. In these the chiral centers preexisting in the substrate are not detached after the controlled
formation of new elements of chirality. They are diastereoselective reactions which are often of prime importance to
the achievement of the total synthesis of natural products.
Most of the strategies may be applied to the resolved or
racemic substrate, and then fit with the proposed extended
definition of asymmetric synthesis.“] A third group of reactions is directly connected with the use of the chiral pool
as source of chiral synthons. Fairly complex chiral molecules can be synthesized by combining small chiral building blocks obtained from cheap natural products (sugars,
amino acids,. . .). This approach does not necessarily create
new asymmetric centers, but involves chemical reactions
with specific protecting groups and reactions compatible
with the stability of some key stereocenters.
Volumes 2 and 3 have the common title “Stereodifferentiating Addition Reactions”. This title, which is not redefined here for the benefit of the newcomer to the field,
originates from the classification of the steric course of
reactions as proposed by Izumi and Tai.”]
Volume 2 begins with a chapter on asymmetric hydroboration by H . C. Brown and P. K . Jadhav. These authors
review the synthesis of chiral compounds by hydroboration of alkenes and further transformations leading to
asymmetric C-H, C-OH or C-C bond formation with ee
values often close to 100%. M. M . Midland then presents
the asymmetric reduction of carbonyl groups by chiral boranes or modified borohydrides. A survey by E. R. Grandbois. S. I . Howard, and J. D. Morrison on asymmetric reduction by modified lithium aluminum hydrides follows,
some examples being of great preparative interest. Chapter
4 (Y. Inouye, J . Oda, and N . Baba) includes reductions
with chiral dihydropyridines, which can be considered as
biomimetic reactions. Chapter 5 (E. L. Eliel) covers the addition of chiral nucleophiles to chiral substrates, mostly as
an application of the Cram rule. In Chapter 6 , G . Solladie
presents asymmetric syntheses based on the addition of
chiral nucleophiles to aldehydes and ketones. The chiral
nucleophiles are either organometallic compounds used in
a chiral environment, anions of chiral sulfoxides, or chiral
ester enolates. Conjugated addition to a,B-unsaturated carbony1 compounds is discussed by K . Tomioka and K . Koga
in Chapter 7 (in those cases where the “chiral help” is
either part of the unsaturated carbonyl compounds or of
the nucleophile). The specific topic of 1,4-addition of organometallic compounds to alkenyl sulfoxides with the sulfur atom as chiral center is dealt with by G. Posner in
Chapter 8. Volume 2 is concluded by a review of the alkylation of imine and enamine salts by D. E. Bergbreiter and
M . Newcomb. These are good methods for the asymmetric
a-alkylation of aldehydes and ketones.
Anyeut. Chem. I n f . Ed. Engl. 25 (1996) No. 9
In Volume 3, four chapters are devoted to the creation
of asymmetric centers via enolate chemistry and related
processes. In Chapter I, D . A . Evans covers the stereoselective alkylation reaction of chiral metal enolates. The various facets of asymmetric aldol reactions are discussed by
C. H . Heathcock in Chapter 2. A review of asymmetric synthesis via chiral oxazolines is given in Chapter 3 by K . A .
Lutomski and A . I . Meyers. while in Chapter 4 D. E. Enders discusses the a-alkylation of chiral hydrazones. Olefin
cyclization processes (mostly electrophilic reactions) are
dealt with by P. A . Bartlett in Chapter 5 (C-C bond formation) and Chapter 6 (carbon-heteroatom bond formation).
These processes allow good control to be introduced into
the relative stereochemistry of monocyclic and polycyclic
systems. In Chapter 7, L. A . Paquette deals with asymmetric cycloaddition reactions, particular attention being paid
to the Diels-Alder reaction. The last chapter of the volume
is devoted to chirality transfer via sigmatropic rearrangements ( R . K . Hill), with special emphasis on the Claisen
rearrangement.
Volume 4 comprises various topics: reference is made to
the chiral carbon pool and also to the use of chiral compounds with asymmetric S, N, P, and Si centers. Chapter 1
(226 pages of the 380 pages) is written by J. W. Scott on
the readily available chiral carbon fragments and their use
in synthesis. A large comprehensive table is included
which should prove especially useful to the chemist who is
planning a synthetic strategy. Practical information such as
the approximate price is given, and many total syntheses
using synthons from the chiral carbon pool are presented
in detail. There follow four short chapters on the chemistry
of chiral compounds with heteroatoms as asymmetric centers (presentation of the compounds and their use in syntheses): Chapter 2 by M . R. Barbachyn and C. R. Johnson
summarizes the routes to various types of chiral sulfur centers and their use in asymmetric synthesis; Chapter 3 ( D .
Valentine Jr.) discusses the methods used t o prepare compounds containing a chiral .phosphorus center. This is an
important field because of the use of phosphanes as ligands in homogeneous catalysis; Chapter 4 (F. A . Davis
and R. H . Jenkins Jr.) then deals with the synthesis and
utilization of compounds with chiral nitrogen centers; the
final Chapter, Chapter 5 , is written by C. A . Maryanoffand
B . E. M a r y a n o f f o n the synthesis and utilization of compounds with chiral silicon centers.
Volume 5 , on Chiral Catalysis, appeared only a few
months ago. It is mostly concerned with organometallic catalysis. Chapter 1 is a general presentation by H . Kagan of
various types of chiral ligands which can be introduced
into a complex. These ligands are classified as mono- o r
polydentate as well as according to the nature of the heteroatom (P, S, N, 0, ...) and location of chirality. In Chapter 2, J. HaZpern discusses the mechanism of asymmetric
catalytic hydrogenation with rhodium complexes. Special
importance is given to kinetic data, which allow the location of the origin of enantioselectivity in the catalytic cycle
to be determined. The application of homogeneous catalyzed asymmetric hydrogenation is the topic of the next
chapter written by K . E. Koenig. One application is the
Monsanto process for the synthesis of (S)-dopa. Efficient
asymmetric reductions of various types of functionalized
olefins are listed, suggesting some applications. In Chapter
4, I . Ojima and K . Hirai review asymmetric hydrosilylation
and hydrocarbonylation. Asymmetric hydrosilylation can
at present give high ee values for the reduction of aromatic
ketones but the enantioselectivity of hydrocarbonylation
must be improved if it is to be used technically. Chapter 5
A n g e w Chem. In!. Ed. Engl. 25 (1986)
No. Y
deals with asymmetric coupling reactions (T. Hayashi and
M . Kumada). Most of the reactions involve the coupling of
Grignard reagents to vinylic halides o r allylic alkylations
in the presence of chiral organometallic catalysts. In Chapter 6, S. Otsuka and K . Tani present catalyzed asymmetric
isomerization of functionalized olefins. The class of reactions which is detailed is the transformation of achiral allylamines into enamines bearing an asymmetric center in
the y-position with respect to nitrogen. The most effective
catalyst is a rhodium/Binap complex; it has recently been
used for the industrial synthesis of citronella1 and menthol.
The next two chapters are devoted to the most efficient
and reliable asymmetric synthesis discovered in the past
five years. The Sharpless reagent for asymmetric epoxidation of allylic alcohols is now widely used in syntheses,
and hundreds of references in the recent literature show
the usefulness of this reaction for the preparation of functionalized compounds in 95-98% ee. In Chapter 7, B. E.
Rossiter describes the synthetic aspects and applications of
asymmetric epoxidation by various methods, and the author gives details of the results obtained with asymmetric
epoxidation by the Sharpless reagent. Applications in the
total synthesis of natural products are listed. In Chapter 8,
M . G. Finn and K . B. Sharpless discuss the mechanism of
asymmetric epoxidation with titanium-tartrate catalysts. In
this relatively long chapter (1 14 pages) structural information on various Ti-complexes (tartrate derivatives as well
as kinetic data) is given. A mechanism is proposed, and the
kinetic resolution of racemic allylic alcohols is also considered. Unpublished data on the results obtained with ligands other than diethyl tartrate are given in a table. N o
major improvements were noticed for these fifty ligands,
so that the tartrates, which were the first to be tested, still
remain the best choice. A useful (and still unpublished)
procedure is described in detail by the authors, namely the
possibility of the routine use of catalytic amounts of titanium-tartrate complexes in the presence of molecular sieves.
This places the Sharpless epoxidation (which is patented)
on the brink of industrial application. Two short chapters
bring the final volume of the series to a close. In chapter 9,
J. B. Jones discusses enzymes as chiral catalysts. This
chapter includes a n introduction to enzymes (classification, main reactions) followed by many examples of various types of asymmetric syntheses, and is a short but excellent presentation of an extremely important area. A few
examples of kinetic resolution are also given. In Chapter
10, asymmetric heterogeneous catalytic hydrogenation is
discussed by K . Harada. Most of the examples given concern either chiral ketoesters, imino esters or enaminoesters
which are hydrogenated in the presence of a metal catalyst.
Stereochemical models, based on the interaction with the
surface are proposed.
In spite of the large number of authors and topics the
complete work appears quite homogeneous in its presentation. Some of the material presented has already been reviewed but, nonetheless, it is very convenient for the practitioner or newcomer to find all the basic information concentrated in one work. Most of the contributions are well
written and very informative, and include the most important literature references. There are only a few mistakes.
The volumes o n stereodifferentiating addition reactions
deal with a field which is almost mature and can be considered as textbook material. By way of contrast, Volume
5 , Chiral Catalysis, is not so satisfactory, since some areas
are not covered, presumably due to lack of space. This is
unfortunate because asymmetric catalysis is developing
rapidly and is on the verge of industrial application.[3’The
849
work by Izumi and Tai on catalytic hydrogenation with
metals modified by tartaric acid is neglected and could at
least have been discussed in Chapter 10. It is a pity that no
section is devoted to catalysis by chiral amines, amino
acids o r small peptides, despite spectacular results being
obtained such as, e.g., the proline-catalyzed cyclization of
trike tone^,'^.'] the alkaloid-catalyzed ketene addition,I6’ and
the asymmetric alkylation with a chiral phase-transfer
Moreover, enzymatic reactions are presented in
only thirty pages. As stated by the author, this chapter
should serve more as an introduction than a comprehensive coverage of the topic because of lack of space. Despite
these criticisms, however, the work as a whole is an invaluable tool for the chemist already engaged in the field, and
should become a reference work for everybody working on
the stereocontrolled synthesis of organic molecules. The
stereochemical nature of the series is well evidenced by the
names to whom the five volumes are dedicated: H . S.
Mosher, A . Horeau, D. Cram, S . Yamada, and V. Prelog.
Asymmetric syntheses and stereocontrolled processes
abound in the current literature and are the topic of many
international meetings and symposia. This collected work
should greatly stimulate the advance of asymmetric synthesis. Perhaps in a few years time a new set of volumes
will be needed in order to reassess the state of the art.
Henri B. Kagan [NB 759 IE]
Universite de Paris-Sud, Orsay Cedex (France)
[ I ] J. D. Morrison, H. S. Mosher: Asymmetric Organrc Reactrons, Prentice
Hall, Englewood Cliffs, NJ. USA 1971; reprint: American Chemical
Society, Washington 1976.
[2] 1. Izumi, A. Tai: Stereo-di~~erentraringReoctmns. Academic Press, New
York 1977.
[3] B. Bosnich: Asymmetric Catalysis (NATO AS1 Series), Martinus Nijhoff,
Dordrecht 1986.
[4] Z . G. Hajos, D. R. Parrish, J. Orq. Chem. 39 (1974) 1615.
[S] U. Eder, G. Sauer, R. Wiechert, Angew. Chem. 83 (1971) 492; Angew.
Chem. In,. Ed. Engl. 10 (1971) 496.
[6] H Wynberg, E. G. J. Staring, J . Am Chem. Soc. 104 (1982) 166.
171 U. H. Dolling, P. Davis, E J J. Grabowski, J . Am. Chem. Soc. 106 (1984)
446.
Air Pollution and Plants. By C . Troyanowsky. VCH Verlagsgesellschaft, Weinheim 1985. x, 298 pp., bound, DM
120.00.-ISBN 3-527-263 10-1
This book contains the papers presented at the Second
European Conference on Chemistry and the Environment,
held in London in 1984 under the auspices of the Federation of European Chemical Societies and the German
Chemical Society. They are concerned with the atmospheric chemistry of pollutants (processes involving the
formation of photo-oxidants, and photo-degradation processes occurring at aerosol surfaces), the direct and indirect effects of pollutants on plants, trees, and the ground
and water systems, and the relevant analytical methods
and monitoring programs.
The papers reflect the wide variety of views that exist
concerning the effects of atmospheric pollution on terrestrial ecosystems, and also a degree of confusion on the
subject, notably with regard to cause-effect relationships.
Many of the contributions are informative, but the book is
by no means representative of all European research in
this field. In particular, there is insufficient information on
850
the basic chemistry involved, and the fact that shortcomings in our understanding of the processes are largely
caused by a lack of adequate analytical methods to provide specific evidence for individual pollutants does not
come out clearly enough. Some of the papers are only reported as abstracts which are not very meaningful by
themselves. The contribution by B. Ulrich (Gottingen) concerning the direct and indirect effects of pollutants on forests, and the resulting changes to the ecosphere, is especially well-written and informative. Ulrich expresses the
view that, although man cannot destroy nature itself, he
can destroy the ecosystems on which it depends, and therefore pollution o f the atmosphere needs to be eliminated as
quickly as possible. An opposite view is given by E. Weise
(Leverkusen), who asks for further clarification and for
priorities to be decided, so as to avoid hasty and mistaken
actions.
Werner Stumm INB 766 IE]
Swiss Federal Institute for Water Resources
and Water Pollution Control,
Diibendorf (Switzerland)
Biological Oxidation of Nitrogen in Organic Molecules.
Chemistry, Toxicology and Pharmacology. Edited by J.
W. Gorrod and L. A . Damani. VCH Verlagsgesellschaft,
Weinheim 1985. 445 pp., bound, DM 150.00.-ISBN 3527-26299-7
Research into the metabolism of organic nitrogen compounds by N-oxidation began about 1920 with the isolation of N-acetylphenylhydroxylamine from the blood of
cats which had been given acetanilide (Ellinger, HoppeSeyler’s Z . Physiol. Chem. I l l (1920) 86). Since then many
nitrogen-containing xenobiotics have been studied, and in
1978 one of the editors of this book, J. W. Gorrod, reviewed progress u p to then in this field of research. The
present volume is concerned with the latest developments,
some of which are extremely interesting, especially with regard to the biochemical pharmacology and toxicology of
N-oxidations.
A short introductory chapter describes the possibilities
of nitrogen oxidation in xenobiotics; the products consist
essentially of hydroxylamines, hydroxamic acids, nitrosoand nitro-compounds, oximes, nitrones and N-oxides.
The rest of the book is divided into nine sections. The
first describes the methods for analyzing N-oxidized compounds, especially those for arylhydroxylamines and tertiary amine oxides. Next, the flavin-containing monooxygenase (“Ziegler’s enzyme”) i s discussed. A series of
short chapters (about four or five pages each) then deal
with pargyline, alicyclic amines, fomocaine, secondary
aromatic amines, N , N-dimethylaniline, cimetidine, ranitidine and (S)-(-)-nicotine. The third section is concerned
with oxidation and formation of aromatic amines, especially chemical carcinogens, and dietary control of the bacterial metabolism of the nitro group. The fourth section
discusses the oxidation of amides and carbamates, especially of the known carcinogen 2-acetylaminofluorene. The
next section deals with the N-oxidation of azaheteroaromatic compounds, and the following one with the oxidation of amidines, imines, triazenes, hydrazine and azo
compounds.
The following two sections, on N-oxidations by prostaglandin-H-synthetase and by the peroxidase-H,O, system,
are highly topical and of particular biological interest owAnqew. Chem. hit. Ed. Engl 25 (1986) No. 9
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