The oxidative coupling of benzylamines proceeds efficiently using salicylic acid derivatives as organocatalysts under an oxygen atmosphere, affording the corresponding N -benzylidenebenzylamines in high yields. Electron-rich salicylic acid derivatives such as 4,6-dimethoxysalicylic acid and 4,6-dihydroxysalicylic acid exhibit excellent catalytic activities for the oxidative coupling of benzylamines to give the corresponding imines. This amine oxidation can also be applied to the synthesis of nitrogen-containing heterocycles such as benzimidazole derivatives. Furthermore, to recycle the catalyst, silica gel supported with 4.7 wt % of 4,6-dihydroxysalicylic acid is prepared, which acts as a recyclable catalyst, oxidizing benzylamine to imine four times successfully.

Metal-free, oxidative four-component Ugi reactions (U-4CRs) were conducted to synthesize dipeptides from two different amines, isocyanides, and carboxylic acids using 2,4,6-trihydroxybenzoic acid catalyst in O2 atmosphere. The organocatalytic U-4CRs proceed via oxidative cross-coupling of benzylamines with other aliphatic or aromatic amines to form imines, followed by condensation with isocyanides and carboxylic acids. The U-4CRs via cross-coupling of amines are rare, and the simple, metal-free procedures are advantageous for further applications in drug and heterocycle syntheses.

Apatite nuclei (ApN) were precipitated by raising the pH of simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. The maghemite (£-Fe 2 O 3 ) particles were attached to the ApN, and the particles were subsequently soaked in SBF adjusted at pH = 7.60, 36.5°C for one day. By this treatment, the ApN induced hydroxyapatite (HA) formation and the £-Fe 2 O 3 particles were encapsulated with HA particles with approximately 12¯m in diameter. The specific surface area of thus-obtained HA/Fe 2 O 3 particles was almost 27 times as large as that of the commercially obtained HA particles. Urease or superoxide dismutase (SOD) was immobilized on the surface of the HA/Fe 2 O 3 particles in ultrapure water, and the particles were collected by using a neodymium magnet. It was indicated that more than 90 % of urease or SOD was collected by using the HA/Fe 2 O 3 particles. By using the urease immobilized on the HA/Fe 2 O 3 particles, furthermore, urea dispersed in buffered solution almost completely decomposed. As the immobilization efficiency of urease increased, the urea decomposition was promoted.

Apatite Nucleus (AN) was attached on the surfaces of maghemite (γ-Fe2O3) particles and soaked them in SBF. By this treatment, formation of bonelike apatite was induced by AN and the apatite covered the whole surface of the γ-Fe2O3 particles. Urease was immobilized on the surfaces of microcapsules and collected by a neodymium magnet. The immobilized urease has an ability of a urea decomposition in an aqueous solution.

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