Current Organic Chemistry, Volume 7, No. 1, 2003
Contents
Carbohydrate
Chemistry
Guest Editor: Zbigniew J.
Witczak
Iron Complexes in Carbohydrate Chemistry Pp.1-12
Aleksander
Zamojski and S–lawomir Jarosz
Carbohydrate Derivatives Containing the
Carbon-Lithium and Carbon-Tin Bonds Pp.13-33
Slawomir
Jarosz and Aleksander Zamojski
1,2-cis O-Glycosylation: Methods, Strategies,
Principles Pp.35-79
Alexei
V. Demchenko
Selective Carbohydrate Recognition by Synthetic Receptors
in Aqueous Solution Pp.81-102
Susanne
Striegler
Abstracts
[Back to top] Iron Complexes in Carbohydrate Chemistry
Formation and synthetic
applications of carbohydrate-iron complexes possessing C-metal bond are
discussed. Some of these intermediates are stable and can be isolated and
characterized. In many instances, however, the sugar carbon-iron complexes
exhibit a limited stability and are directly converted into the final products
without their prior isolation and characterization. Nevertheless, the presence
of such complexes can be inferred from spectral data.
In this review the
emphasis is put on the applications of carbohydrate-iron complexes in the
synthesis of a less common sugar derivatives. Thus, de novo synthesis of
mycaminose, an antibiotic sugar, is described employing an intermediary
amino-dienone tricarbonyliron complex. Sodium (h5-cyclopentadienyl)-dicarbonyl-iron served as
a source for the CO group insertion into derivatives of methyl b-D-glucopyranoside. A general method of
deoxysugar synthesis was proposed starting from monosaccharide aldehydes and
anion obtained from (h5-cyclopentadienyl-carbonyl-triphenylphosphine-acetyl-iron
(“acetyl-iron”). In that manner several derivatives of deoxy-pentoses, -hexoses
as well as a series of 6-deoxy heptoses were obtained. Reactions of acetyl- and
propionyl-iron anions with hexofuranose epoxides led to the heptofuranose
lactones. Also, reactions of sugar aldehydes with anion derived from
“(methylthioacetyl)iron” are described.
The review presents the literature from 1979 (first applications of iron complexes in carbohydrate chemistry) to 2001, inclusively; 39 references.
[Back to top] Carbohydrate Derivatives Containing the
Carbon-Lithium and Carbon-Tin Bonds
Slawomir
Jarosz and Aleksander Zamojski
The monosaccharide
derivatives containing the C-Sn and C-Li bonds are reviewed. Both types of these
organometallics are useful intermediates in the synthesis of variety of
optically pure compounds such as higher carbon sugars, C-disaccharides,
carbocyclic derivatives, etc.
Organometallics
containing the C-Sn bond are usually stable and can be isolated in the pure
form, but their reactivity is low. The tin moiety in such compounds can be
replaced by the lithium atom, leading to derivatives with the C-Li bond. The
latter are highly reactive but unstable. However, the lithium atom in such
unstable organometallics can be replaced with tin moiety, thus providing stable
stannyl intermediates, which can be easily purified. Such a facile mutual
exchangeability of the metal (Li ® Sn and vice versa) makes these sugar
organometallics particularly attractive during stereocontrolled syntheses.
In this review
carbohydrate derivatives containing the metal atom (tin or lithium) placed at
the sp3 carbon atom as well as at sp2 and sp centers (at various positions of
the sugar molecule) are reviewed. In addition, selected derivatives in which
the metal is connected directly to the anomeric center are described.
General methods of
the synthesis of these important organometallic intermediates are evaluated.
Application of lithiated or stannylated monosaccharide derivatives in the
stereoselective syntheses is emphasized. The mechanistic aspects of these
processes are discussed.
[Back to top] 1,2-cis O-Glycosylation: Methods, Strategies, Principles
Alexei
V. Demchenko
The aim of this review is to discuss the accomplishments made in the area of the stereoselective formation of a 1,2-cis glycosidic bond. Importance of this subject derives primarily from the natural occurrence of numerous 1,2-cis-linked oligosaccharides, glycosides, and glycoconjugates, which are widely distributed in living tissues. These compounds are also found in the human milk, in blood group compounds, in bacterial lipopolysaccharide antigens, and many other sources. A great number of reviews and book chapters dedicated to the oligosaccharide synthesis have recently emerged, and therefore general aspects of the glycosidic bond formation are discussed only up to a certain extent. Instead, this review is focused primarily on the glycosylation methods for the synthesis of 1,2-cis glycosides, which are traditionally underrepresented in the literature.
[Back to top] Selective Carbohydrate Recognition by Synthetic Receptors
in Aqueous Solution
Susanne
Striegler
The molecular
recognition of carbohydrates in water is an intriguing subject in view of the
important role of saccharides in biological activities, such as intercellular
recognition, signal transduction or as targets of bacterial/viral infection of
cells. Considerable efforts have been directed toward understanding and
mimicking such recognition processes, and developing effective agents to
control these events. Driven by the need to create very efficient methods to
combine a detectable signal with the recognition process, the past few years
have seen a major push towards practically useful synthetic carbohydrate
sensors.
This review
summarizes the recent achievements upon the preparation of synthetic receptors
for carbohydrate recognition in water. Single molecule sensors based on boronic
acids as well as polymeric receptors for saccharide sensing are discussed.
Current research efforts are summarized, which address the development of
operational sugar sensors for online monitoring and for long-term stability.
Special emphasis is given to sugar sensing probes with a signal detection
system, which is based on ligand exchange. The discussion in this review
further includes polymeric carbohydrate receptors, which generate the sensing
signal by altering the surrounding matrix property of the saccharide
recognition site. Also, the recent developments to prepare carbohydrate
recognition sites with high chiral discrimination ability are highlighted.