Various kinds of N-carboxy-α-dehydroamino acid anhydrides (ΔNCA) were synthesized by the cyclization of N-benzyloxycarbonyl-α-dehydroamino acids, which were corresponded to the proteinic α-amino acids, with thionyl chloride. The obtained Δ NCA derivatives were further applied to the syntheses of the other interesting α -dehydroamino acids and dehydropeptides, inclusive of a few naturally occurring dehydrooligopeptides.
Various organic reactions observed in the course of development process of the photographically useful compounds and their applications are described. The contents are classified into the following seven topics. 1) The Friedel-Crafts type methanesulfonylation of deactivated benzenes, 2) A regioselective synthesis of 2, 5-di (methylsulfonyl) phenol, 3) A practical synthetic intermediate for 4-aryloxy-5-nitro-2-aminophenol, 4) A new deprotection method for levulinyl protecting groups under neutral conditions, 5) N-Methyl-2-dimethylaminoacetohydroxamic acid as a new reagent for the selective cleavage of active esters under neutral conditions, 6) A polymer beads-bound N-methyl-2-dialkylaminoacetohydroxamic acid reagent, 7) A novel photographic assay of 1-phenyl-5-mercaptotetrazole having a formylhydrazino moiety by use of its electron injecting activity toward silver halide.
This article describes the enantioselective synthesis of natural products achieved in the authors' laboratories using optically active O-benzylglycidol as a common building block. Due to its high functionality, its latent symmetric structure, and its ready availability, the glycidol building block exhibited versatile adoptability to allow construction of a variety of natural products.
Syntheses and some reactions of highly coordinate organosilicon compounds as synthetic reagents, substituted by alkoxy groups, are described. Topics are (1) preparations of pentacoordinate allylsiliconates, isolated for the first time, as useful and storable reagents for regio-, chemo-, and stereoselective allylations of carbonyl compounds, (2) stereochemical outcomes of asymmetric allylation with optically active allylsiliconates which are interpreted by a six-membered cyclic transition state, (3) cross-coupling reactions of alkenylsiliconates with organic iodides and triflates catalyzed by a palladium complex in a stereoselective mode, and finally (4) chemo- and stereoselective reductions of carbonyl compounds using alkoxy-substituted hydridosiliconates derived from trialkoxysilane and alkali metal alkoxides or lithium salts of amino alcohols, and new catalytic asymmetric reductions of prochiral ketones using hydridosiliconates.
The review describes about the compounds which can enhance the generation of superoxide (O2-) and hydrogen peroxide (H2O2) in the biological systems and about the novel metal complexes which can have superoxide dismutase activity in vivo. Some compounds are readily reduced by one or two electron (s) to produce their reduced forms. When these reduced forms can react with dioxygen, the compounds often have the potential to increase the production (s) of O2- and/or H2O2 in living cells. The review shows that hypervalent heteropentalenes, 3, 4-diaza-1, 6, 6 a-trithiapentalenes (TTP) and 1, 6-dioxa-6 a-thia-2, 5-diazapentalenes (HEP), are capable of this in studies with electrochemical reactions and Escherichia coli, respectively The hypervalent structures may be essential for enhancement of O2- and/or H2O2 generation in living cells. The review also shows that novel metal complexes, Fe (II) -tetrakis N, N, N'- (2-pyridylmethyl) ethylenediamine (Fe-TPEN) and Fe (III) -tris [N- (2-pyridylmethyl) -2-aminoethyl] amine (Fe-TPAA) act as potent superoxide dismutase mimics in vivo. The iron complexes appear to have the possibility of being applied therapeutically.
PQQ-oxidation of several substrates such as amines, α-amino acids, alcohols, D-glucose, aldehydes, and thiols is investigated. In the oxidative deamination of amines and the oxidative decarboxylation of α-amino acids, a cationic micelle provides a good environment for the reactions The ionic mechanism via carbinolamine intermediate is proposed for the amine-oxidation. Aluminum t-butoxide and aluminum chloride are found to catalyze the oxidation of alcohols with trimethyl ester of PQQ (PQQTME) D-Glucose and thiols are also oxidized by PQQ efficiently to gluconic acid and the corresponding disulfides, respectively Oxidation of aldehydes by PQQ proceeds efficiently in the presence of a thiazolium salt or cyanide ion. Mechanisms of these reactions are investigated kinetically. An efficient NAD+-regeneration system with PQQ and molecular oxygen is found to be applied to HLADH-catalyzed oxidation of alcohols. Finally, synthetic methods of PQQ-model compounds are developed to elucidate the roles of the functional groups of PQQ. The 2-mono- and 2, 9-dicarboxylic acid derivatives 1 b and 1 d and the 1-methylated derivative 1 f are synthesized relatively easily from the intermediates 5 and 4 of the PQQ-synthesis. The 2, 7-dicarboxylic acid derivative 1 e is also synthesized via a combination of the Japp-Klingemann and Fischer indolization.