Current
Organic Chemistry, Volume 9, No. 3, 2005
Contents
a-Amino Acids, b-Amino Alcohols and Related Compounds as Chiral Auxiliaries, Ligands and Catalysts in the Asymmetric Aldol Reaction Pp. 219-235
Jose L. Vicario,
Dolores Badia, Luisa Carrillo, Efraim Reyes and Juan Etxebarria
Rosa M. Ortuno,
Albertina G. Moglioni and Graciela Y. Moltrasio
Ring Contraction Methodology for the Synthesis of
Pyrroles Pp. 261-288
Uday Joshi, Muriel
Pipelier, Sebastien Naud and Didier Dubreuil
Transition Metal-Catalyzed Organic Reactions in
Supercritical Carbon Dioxide Pp. 289-297
Huan-Feng Jiang
Biocatalysis in Supercritical CO2 Pp.
299-315
Tomoko Matsuda, Tadao
Harada and Kaoru Nakamura
Biological Noncovalent Complexes By Mass Spectrometry Pp.
317-324
J. Hardouin and C.M.
Lange
Abstracts
[Back to top] a-Amino
Acids, b-Amino Alcohols and
Related Compounds as Chiral Auxiliaries, Ligands and Catalysts in the
Asymmetric Aldol Reaction
The aldol reaction is regarded as one of the most powerful tools in organic synthesis for the formation of carbon-carbon bonds. Besides, this reaction allows the generation of many stereocenters in the final product, which makes it even more interesting from the synthetic organic chemist point of view. Consequently, an extensive number of methodologies for performing stereoselective aldol reactions have been developed over the last years. In this context, enantiopure a-amino acids, b-amino alcohols or closely related compounds have very often played successfully the role of chirality sources either as auxiliaries, ligands or catalysts in order to exert efficient stereocontrol in the addition step. In this review the use of such chiral reagents in asymmetric aldol reactions will be presented and the most important applications in the field of organic synthesis will be highlighted.
[Back to top] Cyclobutane Biomolecules: Synthetic Approaches to Amino
Acids, Peptides
and Nucleosides
Rosa
M. Ortuno, Albertina G. Moglioni and Graciela Y. Moltrasio
Among the natural or designed products containing
the cyclobutane moiety, amino acids and nucleosides are relevant. Some of these
compounds are receiving much attention due to their biological properties as
antibiotics, and antiviral or antitumoral agents. Synthetic approaches to these
compounds are considered in this review, based on [2+2]- photocycloadditions or
on the use of suitable precursors bearing the pre-formed cyclobutane ring.
Absolute chirality is determined by the use of chiral precursors, i.e.
terpenes, through chemoenzimatic resolutions, or by using chiral reagents and
catalysts. Functionalization of the carbocyclic ring, a feature of crucial
relevance, is the other synthetic challenge to be considered. More of ninety
recent works are referred.
[Back to top] Ring Contraction Methodology for the Synthesis of
Pyrroles
Uday
Joshi, Muriel Pipelier, Sebastien Naud and Didier Dubreuil
Ring contraction of larger rings is one of the important
tools in the repertoire of the methods for the synthesis of pyrroles and has
long been described in the literature. This methodology affords pyrrole
derivatives with varied substituents, which are otherwise difficult to
synthesize. Some of the examples of ring contraction leading to pyrrole have
already been exemplified in various reviews, but there is no review focusing
only the ring contraction strategy. Herein, we wish to focus on the synthesis
of pyrroles by this strategy. The methods are mainly classified on the basis of
the type of the starting heterocycle used. The synthesis of fused pyrrole
systems such as indoles is also included as the special case. Thus, we herein
discuss the methods comprising of the extrusion of an atom or a group of atoms
from the larger ring or the opening of the larger rings and recyclization to
afford the pyrroles.
[Back to top] Transition Metal-Catalyzed Organic Reactions in
Supercritical Carbon
Dioxide
Huan-Feng Jiang
This paper reviews recent progresses of the organic
reactions catalyzed by transition metals in supercritical carbon dioxide (scCO2)
in our group. The reactions include oxidation, reduction, carbonylation,
radical addition, C-C coupling and cycloaddition reactions. All the reactions
can be performed in scCO2 with equal or even better results than in
conventional organic solvents, owing to the high diffusion and low viscosity of
scCO2. The addition of suitable amount of co-solvents in scCO2
is necessary in most reactions, because it not only improves the solubility of
transition metal salts in scCO2, but also regulates the ratio of
products and raises the selectivity as well. Our work demonstrates that scCO2
and its modifier can be used as an alternative solvent for toxic organic
solvents, and thus offers an environmentally friendly medium for the
development of new synthetic methods in green organic chemistry.
[Back to top] Biocatalysis in Supercritical CO2
Tomoko
Matsuda, Tadao Harada and Kaoru Nakamura
Enzymes have been used in non-aqueous media to make
the reactions and the following process more efficient and greener. Here,
recent progress in enzymatic reactions in supercritical carbon dioxide is
reviewed. Hydrolysisesterification, oxidation-reduction and carboxylation are
described, including highly enantioselective reactions.
[Back to top] Biological
Noncovalent Complexes By Mass Spectrometry
J.
Hardouin and C.M. Lange
Mass spectrometry has been used to study noncovalent
protein interactions. Two typical ionizations permit the analysis of fragile
biomolecules : matrix assisted laser desorption ionization (MALDI) and
electrospray ionization (ESI). The gentleness of these techniques allows the
detection of intact noncovalent complexes by mass spectrometry. However, the
analysis success depends on the sample preparation and the instrumental
parameter tuning both in MALDI-MS as well as in ESI-MS. ESI-MS seems to be the
best analytical tool for this study as shown by the large number of published
articles. Mass spectrometry becomes more and more attractive to obtain rapidly
information about multimeric structures and interaction between host and guest.