Gastric H+/K+-ATPase, located in the parietal cell, is responsible for the final step of acid secretion in the stomach. Since omeprazole, a sulfinyl compound, was found to inhibit H+/K+-ATPase in 1983, there has been considerable interest in H+/K+-ATPase inhibitor as a splendid drug for the treatment of peptic ulcer. H+/K+-ATPase inhibitors are classified into two categories. One is an irreversible inhibitor binding to a critical thiol group on the enzyme, such as omeprazole, lansoprazole and NC-1300-O-3, and the other is a reversible K+-competitive inhibitor. In the former, substituted pyridyl derivatives transform in the acid compartments of the parietal cell into the active inhibitor. This paper reviews the development of H+/K+-ATPase inhibitors.
Two new synthetic methods of 5-thioaldopyranosides are described. The first one is substitution of the ring oxygen with sulfur atom via the corresponding acyclic monothioacetals obtained by reaction of pyranoside with dimethylboron bromide and then with thiolacetic acid. Having some limitations in the ring-opening reaction, this method could be applied to disaccharides. The second one is glycosylation with 5-thioaldopyranosyl trichloroacetimidate. Behaviors of synthesized 5-thiopyranoside derivatives toward some glycosidases were also described.
This review describes the studies on the total syntheses of the natural products, particularly alkaloids and terpenes, which involves the determination of absolute configurations of emetine, yohimbin and reserpine. It has been attempted in principle that the synthesis should be developed by utilization of the new reactions originated in our own laboratory. The successful syntheses are demonstrated by “one-step synthesis of β-carboline derivatives”, “development of a new synthetic method for 3, 3-disubstituted oxindole derivatives, which method was extended to the synthesis of various indole alkaloids through a common intermediate”, “the total synthesis of strychnos, aspidosperma and schizozygane alkaloids by photo-isomerization of 1-acylindole to 3-acylindolenine”, “the crisscross annulation for syntheses of heterocycles and the natural products” and “bis trimethylsilyl enol ether has been utilized as a 'masked acyl anion'for the synthesis of terpenses and the biologically active cyclic lactones”.
Recent studies on acid and redox catalyses of heteropoly compounds in both homogeneous and heterogeneous systems are reviewed. Acid and redox properties of heteropoly compounds are briefly summarized. Recent applications of heteropolyacids to homogeneous acid-catalyzed reactions such as polymerization of tetrahydrofuran, glucoside synthesis, and aldehyde trimerization are interesting. In heterogeneous system, an insoluble acidic Cs salt, Cs2.5H0.5PW12O40, is much more active for liquid phase alkylation than Nafion, HY-zeolite, H-ZSM-5, and SO42-/ZrO2. Pseudoliquid phase behavior of H3PW12O40 brings about a high activity for alkylation of phenol. Homogeneous oxidation using molecular oxygen and phase-transfer catalysts for oxidation using H2O2 are attractive. In heterogeneous oxidations, the catalytic properties of oxidation of aldehyde and oxidative dehydrogenation has been explained by the concept of the surface-type and bulk-type (II) reactions. Finally, catalyses of novel types of complexes with organometallics and combination system with transition metals are described with respect to oxidation of olefins, hydroformylation, and reductive carbonylation.
It has been well documented that palladium complexes catalyze versatile and useful reactions. Contemplation of these reactions from the standpoint of polymer synthesis has brought new polymerizations, which are reviewed in this article including topics of ring-opening polymerization, polycondensation, polyaddition, and addition polymerization. 1) A new type of ring-opening polymerization, whose key intermediates were π-allyl palladium complexes, was developed. Especially, for the polymerization of cyclic carbamates was designed and achieved an unusual mode that propagating ends multiply at every step of propagation. The produced polyamines had hyperbranched dendritic structures incorporating the initiator as the core. 2) Aromatic polymers such as poly (phenylene vinylene) s, polyphenylenes, and polyamides were prepared by the Heck reaction and Pd-catalyzed cross-coupling reactions. 3) Electrophilic palladium complexes initiated vinyl polymerizations of styrene, methyl propiolate, norbornene, etc. as well as alternating copolymerizations of some alkenes with carbon monoxide. Bromo (methyl) palladium-phosphine complexes initiated living aromatization polymerizations of 1, 2-diisocyanoarenes. 4) A cyclic compound having a Si-Si bond, 1, 2-disilacyclopentane, was polymerized with the aid of a Pd (0) complex.
Chemical modification of polymers containing pendant chlorine was investigated using phase transfer catalysis, which is a very simple and convenient method for polymer synthesis as well as organic syntesis. The reactions of polymers containing chlorine such as poly (chloromethylstyrene), poly (epichlorohydrin), and poly (2-chloroethylvinyl ether) with various nucleophilic reagents composed from alkalimetal salts were carried out under three different reaction systems, solid-liquid, liquid-liquid, and solid-liquid-solid systems in the presence of phase transfer catalysts (PTCs). The reactions were strongly influenced by the kind of PTC, concentration, concentration of reagent, reaction solvent, and the combination of PTC and nucleophilic reagent. From these results, it was found that the reactions proceeded smoothly to give the corresponding polymers under mild conditions. Synthesis of some functional polymers such as photosensitive polymers, multi-functional polymers, and solar energy storage polymers with pendant norbornadiene moieties was performed using PTC based on the above information.