Participation of a neighboring group provides anchimeric assistance in carbocation reactions. In other words, intramolecular attack by the group towards a reaction (cationic) center forming in the rate-determining step is accelerated, while intermolecular attack by solvent is not. This idea is related to the factors which have been suggested to the mechanisms of enzyme-catalyzed reactions. Several recent reactions of synthetic significance and bioorganic importance are explained on the related idea. The reactions involve anchimerically-assisted solvolysis, intramolecular lactonization and thiolactonization, nucleophilic attack on cyclopentyl p-nitrophenyl-methyl-sulfonium compounds, hydrolysis of sulfonamides assisted by a neighboring carboxyl group, some free radical reactions in steroid systems, Norrish photochemical cleavage of a penicillin thioether, cyclodextrin-catalyzed aromatic substitution, and reactions of penicillin sulfenic acid with C6 amide side chain.
Two-phase reactions are reviewed which consist of liquid-liquid and solid-liquid phase systems with quaternary ammonium and phosphonium salts and crown ethers as phase transfer catalysts. Both the working mechanism and the synthetic applications of the phase transfer reactions are given including carbene reactions, C-alkylations, nucleophilic substitutions, ylide reactions, oxidation and reduction, and others.
Synthetic works on lactonic Lythraceae alkaloids were reviewed according to the following articles : synthetic approaches to the alkaloid, Mannich reaction of isopelletierine and arylaldehydes, total syntheses of biphenyl ether-type alkaloids, and total syntheses of biphenyl-type alkaloids. The Mannich reaction of isopelletierine with a ylaldehydes under alkaline condition afforded cis-4-arylquinolizidin-2-ones as a kinetically controlled product, which then isomerized into the corresponding trans-quinolizidines. On the basis of the above observation, the total syntheses of the trans-quinolizidine-type alkaloids such as decaline, desmethyldecaline, methyldecinine, and decinine, and those of the cis-quinolizidinetype alkaloids such as vertaline, methyllagerine, lagerine, and methyldecamine were accomplished.
The diseases caused by the ingestion of mycotoxins are known as mycotoxicosis. Mycotoxins are occasionally very hazardous to us and domestic animals when we and animals take daily foods or feeds infested by toxin-producing fungi. Most mycotoxins are hepatotoxic or nephrotoxic however some of them cause neurologic disease of animals. For instance, citreoviridin is a yellow metabolite Penicillium citreo-viride and causes paralysis in the laboratory animals often followed by convulsion and respiratory arrest. This toxin is suspected by Japanese researchers to be a probable causative factor for acute cardiac beriberi. In this article, a general concept on mycotoxicosis is firstly related and the outline of our study on the tremorgenic toxins is then described. In addition to fumitremorgin A and B which are the tremorgenic toxins newly isolated from Aspergillus fumigatus in our laboratory, the isolation of verruculogen, roquefortin and paxilline have been reported. The structural relations between these toxins and their biological activities are also reviewed.
In connection with a program directed toward the biogenetic type synthesis of bromine containing terpenoids, we have searched a new reagent system and found that 2, 4, 4, 6-tetrabromocyclohexadienone (TBCO) is effective for bromination of polyenes. Reaction fashion of TBCO can be divided into four types. 1. Dibromination, , 2. Brominative cyclization, 3. Bromo etherification of polyene alcohol and ketone, and 4. Bromohydrin formation in the presence of ROH. Details are described.
Nylon was industrially produced by du Pont for first time shortly before World War II. Hexamethy lenediamine (HMD) is a nylon-66 intermediate. Many reports on manufacturing process for HMD have been published and almost all of them now in industrial process go through the three routes, namely via adiponitrile (ADN) by using AN. butadiene or ADA as the starting material. Now among them, the method employing ADA is used most widely, but AN electrolytic hydrodimerization process and new hydrocyanation process for reacting butadiene and hydrogencyanide are developed to eliminate the defects of conventional methods, New hydrocyanation process was recently developed by du Pont and is now believed comercialised.