This article reviews results on double Michael reaction of Diels-Alder type. The review is recorded in four sections ; (i) intermolecular double Michael reaction, (ii) bicycleannulation, (iii) intramolecular double Michael reaction, and (iv) synthesis of heterocyclic compounds having an angular nitrogen. In all sections, applications to syntheses of natural products are briefly discussed.
This article reviews the recent advances in the intramolecular Diels-Alder reactions of furans, which include the reactions with furan as a diene (type I), furan as a part of diene (type II), and furan as a dienophile (type III). This review involves the analysis of the important controlling factors in these reactions as well as their application to the natural product synthesis.
The level theory of protein structure ; module and domain theory in connection with the molecular evolution will become a useful theory for designing new functional proteins. Chemical and enzymatic modification of proteins is a useful technique. Site directed mutagenesis is extensively used for the conversion of amino acid residues of enzymes. Some of the examples gave successful results for the increase of enzymatic activity or heat stability. Instead of changing amino acids one by one, very recently a hybrid enzyme and multi enzyme peptides are designed and produced. Many proteins produced in E. coli are often inactive because of the failed conformation. One of the resolution of this problem is to secrete the products into culture media. Secretary production of protein by yeast is emphasized. Recent production of proteins by yeast gave a good prospect, but many things remain vague.
The regulation of food intake is conducted by the feeding and satiety centers in the hypothalamus, part of the brain. Blood born materials such as glucose, insulin, free fatty acids, and glucagon, which are related to metabolism, are known to be involved in the induction of hunger or satiety. Behavior and electrophysiological experiments have shown that these and other humoral factors act as hunger and satiety signals, through the chemosensitive neurons located in the two centers. To identify other blood factors that might affect body weight by controlling feeding, blood from rats in various stages of food deprivation was analyzed for its constituents. Two short chain sugar acids, 3, 4-dihydroxybutanoic acid (2-deoxytetronic acid, 2-DTA) and 2, 4, 5-trihydroxypentanoic acid (3-deoxypentonic acid, 3-DPA), were isolated by a gas chromatograph-mass spectrometer-computer system. Their effects on rat feeding behavior and on neuron activity were investigated. Injections of 2-DTA into the rat third cerebral ventricle suppressed food intake. The same amounts of 3-DPA elicited feeding. The activity of chemosensitive neurons was suppressed by 2-DTA in the feeding center and facilitated in the satiety center. The effect of 3-DPA was just opposite on the neurons in these two centers. High correlation between modulation of feeding behavior and changes in chemosensitive neuron activity suggested that 2-DTA may act as an endogenous satiety substance and 3-DPA as a hunger substance. The effect of 3-hydroxybutyric acid and other related substances were also verified and discussed.
Anionic living polymerization is the most excellent method to prepare homopolymers and block polymers with controlled molecular weights and very narrow molecular weight distributions. However, functional monomers are unable to be directly polymerized with anionic initiators to generate functional polymers of well-defined structures because initiators and propagating ends react with the functional groups. Recently, it was found that styrene derivatives bearing functional groups, such as hydroxyl, amino, formyl, and carboxyl groups, were polymerized with anionic initiators to afford living polymers at low temperature by masking the functional groups with trialkylsilyl groups and other suitable protective groups. Removal of the protective groups was quantitatively performed by acid treatment of the polymers produced. Thus, by means of protection method and anionic living polymerization, tailor-made functional homopolymers and block copolymers of these functional monomers with styrenes and dienes were synthesized. Various types of microphase separation of the functional block copolymers were observed by electron microscopic measurement.
Various aspects of trimethylsilyldiazomethane (Me3SiCHN2, TMSCHN2) in organic synthesis as a stable and safe substitute for hazardous diazomethane are reviewed in the following items : 1) properties, 2) preparations, 3) use as a reagent for introducing a C1-unit, and 4) use as a [C-N-N] azole synthon.