A subtle change in catalyst structure can sometimes improve catalytic activity dramatically, as we found in our recent study on a-aminoxylation, tandem O-nitroso aldol/Michael reactions, and Mannich reactions catalyzed by the siloxyproline 4, a highly active proline surrogate (Scheme 1).[1] The simple introduction of a siloxy group into the proline structure leads to an increase in the catalytic activity, thus allowing a decrease in catalyst loading and shorter reaction times, without compromising the enantioselectivity, and is accompanied by broadening of the substrate scope. This higher activity can be attributed to the increased solubility of 4 in organic solvents. The fact that the substitution of a hydroxy group for a siloxy group can dramatically affect catalytic activity prompted us to investigate other catalytic systems, and these investigations led us to the diphenylprolinol silyl ether 2. The parent diphenyl-2-pyrrolidinemethanol (1, diphenylprolinol), a commercially available amino alcohol developed by Corey and co-workers, has proved to be a very useful ligand for asymmetric synthesis: B-alkylated oxazaborodine is a useful catalyst for the CBS reduction, [2] while an effective, asymmetric Lewis acid catalyst prepared from B-aryl oxazaborodine and a Brønsted acid promotes the Diels-Alder reaction of a broad range of substrates with excellent enantioselectiv-

Going green: The synthetically very important aldol reaction can proceed in water without a metal catalyst with excellent enantioselectivity. The key to the reaction is a small, synthetic organic catalyst based on trans‐hydroxyproline with a siloxy group. Thus, this method is an environmentally friendly process for the synthesis of chiral molecules.

A method for preparing nanoparticles of a water‐insoluble drug that are suitable for administration to the human body has been established. A reprecipitation method was used to fabricate 50 nm nanoparticles of dimerized SN‐38, an anticancer camptothecin derivative, that form stable aqueous dispersions and can penetrate into cancer cells to inhibit cell proliferation more potently than irinotecan.

A subtle change in catalyst structure can sometimes improve catalytic activity dramatically, as we found in our recent study on a-aminoxylation, tandem O-nitroso aldol/Michael reactions, and Mannich reactions catalyzed by the siloxyproline 4, a highly active proline surrogate (Scheme 1).[1] The simple introduction of a siloxy group into the proline structure leads to an increase in the catalytic activity, thus allowing a decrease in catalyst loading and shorter reaction times, without compromising the enantioselectivity, and is accompanied by broadening of the substrate scope. This higher activity can be attributed to the increased solubility of 4 in organic solvents. The fact that the substitution of a hydroxy group for a siloxy group can dramatically affect catalytic activity prompted us to investigate other catalytic systems, and these investigations led us to the diphenylprolinol silyl ether 2. The parent diphenyl-2-pyrrolidinemethanol (1, diphenylprolinol), a commercially available amino alcohol developed by Corey and co-workers, has proved to be a very useful ligand for asymmetric synthesis: B-alkylated oxazaborodine is a useful catalyst for the CBS reduction, [2] while an effective, asymmetric Lewis acid catalyst prepared from B-aryl oxazaborodine and a Brønsted acid promotes the Diels-Alder reaction of a broad range of substrates with excellent enantioselectiv-

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