Selenium and tellurium isologs of carboxylic acid derivatives are compounds of considerable spectroscopical and synthetical interest. However, the study of the isologs is still a relatively unexplored field compared with thio- and dithiocarboxylic acid derivatives, because of their thermal instability. This review deals with the synthetic methods and reactions of the isologs reported in the literatures up to the end of 1984.
The synthesis of indolizine derivatives and their related compounds using ketene dithioacetals is described. This review is concerned with following five items : 1) the 1, 5-dipolar cyclization ; 2) the reaction of picolinium salts with ketene dithioacetals ; 3) the reaction of 2-pyridyl ketene dithioacetals with α-halocarbonyl compounds ; 4) the reaction of pyridinium or isoquinolinium ketene dithioacetals ; 5) the reaction of N-imines or S-imine with ketene dithioacetals.
Lipoic acid is a coenzyme for the oxidative decarboxylation of α-ketoacids in living systems. In this article we describe some applications of lipoic acid derivatives to organic reactions utilizing its redox function. Lipoamide and its polymer derivatives were demonstrated to work as acyl carriers to form amides by the combination of their reductive acylation and oxidative acyl transfer reactions. Dihydrolipoamide, a reduced form of lipoamide, produced an active complex with ferrous ion which was effective for the selective reduction of N-O linkages in hydroxylamines, isoxazolidines, isoxazoles, and nitrobenzenes under mild conditions. Across a polyglutamide membrane having lipoamide structure, a redox reaction proceeded presumably by a thiol-disulfide exchange reaction between polymeric lipoamide units, which worked as electron carriers.
Methoxybenzyl (MPM) protecting groups for hydroxy function were readily and efficiently removed with DDQ in CH2Cl2-H2O at room temperature. Under these neutral conditions, other usual protecting and functional groups remained unchanged. Dimethoxybenzyl (DMPM) groups were more reactive than MPM with DDQ. This article deals not only with the deprotection of MPM and DMPM with selectivities among MPM, DMPM, benzyl groups, and other groups, and with some extensions such as intramolecular oxidative and kinetic acetalizations, but also with some applications in the synthetic study of macrolide and polyether antibiotics from D-glucose.
Mineral oils are made by refining crude oils with physical operations. On the other hand, synthetic oils are products made by combining low molecular weight components from mineral oil or natural oils and fats via various chemical processes. Those are classified into several categories such as synthetic hydrocarbons (α-olefin oligomer, alkylbenzene, etc.), esters (diester, polyol lester, phosphate, silicate, etc.), ethers (polyalkyleneglycol, polyphenylether) and others (silicone, fluorinated compounds, etc.). Some synthetic fluids show better properties in which mineral oils are poor ; for examples, in viscosity-temperature relations, low tempreature fluidities, high temperature stabilities, fire resistances, etc. Recently, these synthetic oils are getting more important in connection with energy conservation or development of high performance machines. They are applied mainly to aircraft gas turbine oils, automotive engine oils, hydraulic oils, compressor oils and gear oils. In this review, synthetic lubricating oils are introduced for research chemists and chemical engineers of organic syntheses.
This paper reviews the progress in the technology for manufacturing 5'-inosinic and 5'-guanylic acids as flavor-enhancing agents. It is only past 25 years from the beginning of their commercial production. Today, there are two ways for their production : One is degradation of ribonucleic acid from yeast and the other, fermentation from sugars using bacterial mutants. It is difficult to say now which process is better, because both processes include some severe problems to solve for the further technological development. The keys for the further development of the degradation process are (a) availability of ribonucleic acid from methanol bacteria produced as single cell protein, (b) development of a bioreactor consisting of immobilized enzyme systems, and (c) evaluation of utility values of 5'-uridylic and 5'-cytidylic acid as the byproducts. The keys for the fermentation process are (a) increase in the productivity of nucleosides or 5'-nucleotides by strain improvement by means of gene engineering techniques, and (b) development of a bioreactor using immobilized cells. They are now on the way of research and development in the third stage of the progress in the technology for manufacturing flavor-enhancing 5'-ribonucleotides.