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A series of star-shaped poly(lactic acid)s with carboxylic acid terminal groups have been synthesized by direct poly-condensation of lactic acid in the presence of a poly-carboxylic acid core molecule with triphenylphosphonium trifluoromethanesulfonate (TPP-T) catalyst. These star-polymers had thermal properties not very much different from those of star-shaped poly(lactic acid) with hydroxyl terminal groups and linear poly(lactic acid), irrespective of the structure of the core molecule and number of polymer arms. Solubility and degradability of these star-polymers were, however, greatly enhanced compared to those of star-polymers with hydroxyl terminal groups and increased depending on the number of polymer arms. From the star-shaped polymers, a variety of ammonium salts and the corresponding carboxyamides were successfully prepared.

Synthesis of LL-lactide with high chemical, diastereomeric, and enantiomeric purities was achieved by depolymerization of oligo(lactic acid) in the presence of an onium salt catalyst.

The novel doubly borylated enolate is identified as an intermediate of the double aldol reaction of acetate esters. As a precursor to the formation of the doubly borylated enolate, carbon-bound boron enolates of carboxylic esters are spectroscopically characterized for the first time. When 2,6-diisopropylphenyl acetate (10d) is treated with c-Hex(2)BOTf (1.3 equiv) and triethylamine (1.5 equiv) in CDCl(3), the corresponding mono-enolate is formed as a mixture of oxygen- (11d) and carbon-bound (12d) forms in 71% and 20% yields, respectively. The structures of these enolates have been unambiguously determined by NMR spectroscopy. Investigation of the enolization of a series of substituted aryl acetates shows that the steric factor of the acetate affects the degree of the mono-enolate (as a mixture of oxygen- and carbon-bound enolates) and the doubly borylated enolate formation. Studies also revealed that oxygen- and carbon-bound boron enolates exist as equilibrium mixtures and that a proton transfer process occurs between oxygen- and carbon-bound enolates. The doubly borylated enolate formation is general for a variety of carbonyl compounds. Besides acetate esters, carbonyl containing compounds, such as acetic acid, dimethylacetamide, methoxyacetone, and 3-acetyl-2-oxazolidinone, also produce the doubly borylated enolates when treated with c-Hex(2)BOTf (2.5 equiv) and triethylamine (3.0 equiv). A plausible pathway of the double aldol reaction involving a carbon-bound boron enolate as a key intermediate is proposed.

The synthesis of BMPD, 1,3-bis(2-methylferrocenyl)propane-1,3-dione, was achieved via the Claisen condensation of a homochiral ferrocenecarboxylate and an acetylferrocene derived from the same chiral formylferrocene. Several metal complexes were prepared to exemplify the complexation ability of BMPD. A BMPD-yttrium complex was found to act as a new catalyst for silylcyanation of aldehydes with remarkable efficiency. As little as 0.2 mol% of the complex catalyzed the reaction of benzaldehyde and cyanotrimethylsilane to afford the cyanohydrin in 95% yield with 87% ee.

The remarkable catalysis of Bu2SnO for nitrone formation in the nitrone-olefin cycloaddition reaction has been discovered, and has led to the development of a general method for the synthesis of N-unsubstituted isoxazolidine derivatives.

The synthesis of BMPD, 1,3-bis(2-methylferrocenyl)propane-1,3-dione, was achieved via the Claisen condensation of a homochiral ferrocenecarboxylate and an acetylferrocene derived from the same chiral formylferrocene. Several metal complexes were prepared to exemplify the complexation ability of BMPD. A BMPD-yttrium complex was found to act as a new catalyst for silylcyanation of aldehydes with remarkable efficiency. As little as 0.2 mol% of the complex catalyzed the reaction of benzaldehyde and cyanotrimethylsilane to afford the cyanohydrin in 95% yield with 87% ee.

Bis-oxazolines (1–7) prepared from diethyl malonate and chiral amino alcohols were converted into their Cu(II) complexes which, upon activation, exhibit high enantioselectivity of up to 99 %ee for catalytic cyclopropanation of olefins.

The remarkable catalysis of Bu2SnO for nitrone formation in the nitrone-olefin cycloaddition reaction has been discovered, and has led to the development of a general method for the synthesis of N-unsubstituted isoxazolidine derivatives.