Current Organic Chemistry, Volume 6, No. 6, 2002
Bioorganic
Chemistry of Nyctinastic Leaf-movement using synthetic probe compounds Pp. 493-505
Minoru
Ueda, Noboru Takada, and Shosuke Yamamura
Applications
of Heteroarylboron Compounds to Organic Synthesis Pp. 507-521
Minoru
Ishikura
Cleavage
and Isomerization of RNA Phosphodiester Bonds: Nucleoside Phosphotriesters and
Chimeric Ribo/2´-O-Methylribo Oligonucleotides as Tools for Mechanistic Studies
Pp. 523-538
S.
Mikkola, (the late) M. Kosonen and H. Lِnnberg
Alkynyl
– Oxiranes and Aziridines: Synthesis and Ring Opening Reactions with Carbon
Nucleophiles Pp. 539- 570
F.
Chemla and F. Ferreira
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Bioorganic
Chemistry of Nyctinastic Leaf-movement using synthetic probe compounds
Minoru
Ueda, Noboru Takada, and Shosuke Yamamura
Most
legumes close their leaves in the evening, as if to sleep, and open them in the
morning. This is called nyctinasty, and such a circadian rhythmic movement has
been known to be controlled by their biological clocks. We have identified several
bioactive substances that regulate this leaf-movement, and our recent studies revealed
the mechanism for the control of nyctinasty by the biological clock. _ In this
review, we will show two examples of our attempts for the bioorganic study of
plant leaf-movement using synthetic probe compounds. One is the direct
observation of the target cell for leaf-movement factor by fluorescence-labeled
probe compounds and the other is the chemical studies on the historical
problem, “ Why does the plant sleep?”, by artificial leaf-opening substance.
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Applications
of Heteroarylboron Compounds to Organic Synthesis
Minoru
Ishikura
This report deals with our recent results concerning the
reaction and synthetic application of boron-substituted heteroaromatic
compounds; (1) palladium-catalyzed cross-coupling, carbonylative cross-coupling
and tandem cyclization cross-coupling reactions with dialkylpyridylboranes and
indolylborates, and their use in the preparation of heterocyclic derivatives
and (2) the synthetic application of an intramolecular alkyl migration process in
indolylborates for the construction of more elaborate indole derivatives.
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Cleavage
and Isomerization of RNA Phosphodiester Bonds: Nucleoside Phosphotriesters and
Chimeric Ribo/2´-O-Methylribo Oligonucleotides as Tools for Mechanistic Studies
S.
Mikkola, (the late) M. Kosonen and H. Lِnnberg
Phosphodiester bonds of RNA undergo in aqueous solution two
intramolecular transesterification reactions: cleavage to a cyclic
2´,3´-phosphate and isomerization to a 2´,5´-phosphodiester. The reaction is
initiated by a nucleophilic attack of the 2´-hydroxy group on the phosphate,
which results in formation of a pentaco-ordinated phosphorane species. This
phosphorane intermediate may then decompose to either the cleavage or isomerization
products. The reaction system is subject to several different type of catalysis,
and under given conditions, different mechanisms may be concurrently utilized.
The present review discusses the approaches where nucleoside
3´-phosphotriesters have been used as a model for the neutral ionic form of
phosphodiesters to elucidate the mechanistic details of the transesterification
of RNA phosphodiester bonds. Transesterification of the phosphodiester bonds
within oligonucleotidic substrates is also influenced by the molecular
environment of the scissile bond. The secondary structure influences on the
reactivity of RNA phosphodiester bonds either by retarding the rate of cleavage
or enhancing it. These effects are discussed in the light of the mechanisms
described above.
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Alkynyl
– Oxiranes and Aziridines: Synthesis and Ring Opening Reactions with Carbon
Nucleophiles
F.
Chemla and F. Ferreira
Syntheses of alkynyl– oxiranes and aziridines are
rewieved. These compounds can serve as substrates in ring opening reactions
with carbon nucleophiles to give allenyl– or homopropargylalcohols and amines.