This review describes stereoselective reactions of oriented prochiral substrates in the following chiral environment : (1) chiral molecular aggregates of electrolytes, micelles, bilayers and cholesteric liquid crystals, (2) chiral crystals and clathrate crystals, (3) chiral inclusion compounds of crown ethers, cyclic peptides and cyclodextrins, and (4) globular proteins of avidin and bovine serum albumin.
Recent progress in regioselective carbon-carbon bond forming reactions involving “ambident substrates” has been reviewed with 308 selected references. This article is divided into two parts, Part 1 concerns the reactions of ambident nucleophiles which mainly include the di-anions of enolates and the asymmetric allylic carbanions. Part 2 involves the reactions of ambident electrophiles which are represented by α, β-unsaturated carbonyl systems, the SN 2' reactions of allylic alcohol derivatives and the epoxy compounds containing a nucleophile in the same molecule. Some plausible explanations and controlling factors of these regioselectivities are summarized.
It is pointed out that fragmentation reactions are important synthetic methodology for building up unsaturated compounds. It is also suggested that studying the fragmentation reactions in organic chemistry will contribute to the understanding of one aspect of life processes which is featured by the fragmentation reactions of biological substances in terms of unsaturated bond formations and simultaneous gain of entropy in the products.
Methodologies for C-nucleoside synthesis are classified into three types : (1) chemical transformation of naturally occurring C-nucleosides, (2) elaboration of nitrogen heterocycles onto carbohydrate structures, (3) synthesis starting from non- carbohydrate precursors. This article reviews the synthesis of types 1 and 2.
Many kinds of yeasts are known to show sexual reproduction in their life cycles. In the sexual process of certain species, conjugation between two mating-type cells is observed. The presences of regulating substances, mating pheromones, in the process have been demonstrated in several yeasts. From an ascomyceteous yeast, Saccharomyces cerevisiae, we have isolated a peptide, α substance-IA, which regulates sexual agglutination in the mating reaction, and revealed its structure as a dodecapeptide. We have also isolated a lipopeptide, rhodotorucine A, from a heterobasidiomyceteous yeast, Rhodosporidium toruloides as a factor to induce mating tube formation. Rhodotorucine A was found to be a novel lipopeptide having a farnesyl side chain. In this article, chemical studies of these mating pheromones are reviewed togather with the related works.
The reactions of triphenylphosphine -thiocyanogen (TPPT), prepared by a combination of equimolar amount of triphenylphosphine and thiocyanogen, with various nucleophiles are reviewed. It can be classified by the following two features: a) as observed in the reaction with alcohols, carboxylic acids, and epoxides, nucleophilic attack on the phosphorus atom of TPPT followed by substitution of the SCN anion on the adjacent carbon to oxygen atom of the intermediate with elimination of triphenylphosphine oxide, giving the thio-and/or isothiocyanates (Type A) and b) as observed in the reaction of amines, organometallic compounds, indoles and pyrroles, nucleophilic addition to the -N=C=S carbon of TPPT, giving thiocarbamoylated compounds (Type B). Synthetic utilities of TPPT are also summarized.
By whom are research and development promoted ? What is the most important factor in order to succeed in the research activity ? These questions have ever been discussed by many people. In the sixties, a lot of new petrochemical processes were developped and commercialized by aggressive innovators and venture companies. What is their driving force ? The typical two research chemists, W. F. Brill and J. Kollar, who were the good rivals during the past 20 years, and an unique company, Halcon, were picked up in this article to answer above questions.