Current Organic Chemistry - Volume 6, Issue 6, 2002

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.

This report deals with our recent results concerning the reaction and synthetic application of boronsubstituted 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.

Phosphodiester bonds of RNA undergo in aqueous solution two intramolecular transesterification reactions: cleavage to a cyclic 27',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 pentacoordinated 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.

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.