Search

The original flavopeptide catalyst, 3-FlC2- l -Pro- l -Tyr- l -Asp-Ado-NH-PS (Fl-PepLLL), and its diastereomers including Fl-PepDDL, Fl-PepLDL, and Fl-PepDLL were synthesized to investigate the correlation between their catalytic activity and stereochemistry. The results and related computations showed the importance of intramolecular hydrogen bonds involving the Asp residue in their 4a-hydroperoxy forms for the catalysis.

We have designed and synthesized an iridium(III) complex of pincer type imidazo[1,5-a]pyridine ligand. The complex has a broad absorption band and shows the yellow emission in solution. When the complex was used as a photocatalyst in the visible-light-induced oxidative coupling reaction of benzylic amines, the corresponding imines were obtained in quantitative yields.

Riboflavin tetramethacrylate (RFlTMA) was prepared as a flavin monomer and copolymerized with ethylene glycol dimethacrylate (EGDMA) under polymerization-induced phase separation conditions. The resulting flavin-containing mesoporous network polymer, poly(RFlTMA-co-EGDMA), was found to be a more effective catalyst than riboflavin tetraacetate (RFlTA), a soluble analogue, for aerobic hydrogenation of olefins despite its heterogeneity, which allowed for its multiple recovery and reuse through simple filtrations and washings without loss in catalytic activity. In addition, the polymeric flavin was demonstrated to be utilized also as an effective photocatalyst in the oxidation of benzyl alcohols.

Clothespin-shaped bisflavin compounds 1 bearing doubly linked 3,3′:10,10′-methylene spacers exhibited significant enhancement of specific association with a variety of neutral aromatic compounds in DMF under electroreduction conditions. This specificity could be rationalized by the ‘electric clip motion’ of intermediate bis-anion radical species.

Optically active bis(homoallenyl)amines bearing two chiral axes with the same sense of axial chirality were prepared by a one-pot, palladium-catalyzed sequential homoallenylation of primary amines with 2,3-allenyl phosphates.

A series of bisflavinium perchlorates linked with methylene spacer at N 10 -position exhibit high catalytic activities for the oxidation of sulfides with hydrogen peroxide affording the corresponding sulfoxides. The kinetic studies revealed that the reaction rates are dependent on the spacer length of the catalysts due to their specific intramolecular electrochemical behaviors.

Tungstate-catalyzed oxidation of O-tert-butyldimethylsilyl (O-TBDMS) protected (R)-3-hydroxypyrrolidine ((R)-2), derived from trans-4-hydroxy- l -proline, gave O-TBDMS protected (R)-3-hydroxy-1-pyrroline N-oxide ((R)-1), which is a new chiral precursor for the synthesis of Geissman-Waiss lactone. The enantiomeric nitrone (S)-1 was also prepared by the oxidation of (S)-2 derived from l -malic acid.

Palladium catalyzed carbonylations of allyl phosphates and allyl acetates give β,γ-unsaturated esters efficiently. The latter reaction requires bromide ion as a co-catalyst.

Quinolines and isoquinolines are hydrogenated selectively in the nitrogen-containing ring by means of carbon monoxide and water in the presence of catalytic amount of rhodium carbonyl cluster.

Palladium catalyzed reaction of allyl acetates with azide ion gives allyl azides, which are readily converted into the corresponding primary allylamines upon treatment with PPh 3 /NaOH.

Palladium-catalyzed reaction of allyl esters with hydroxylamines gives N-allylhydroxylamines, which are readily converted into secondary allylamines upon treatment with zinc powder in a dilute HCl solution.