Takehisa Kunieda

A new reagent for activating carboxyl groups: diphenyl 2-oxo-3-oxazolinylphosphonate

Abstract Diphenyl 2-oxo-3-oxazolinylphosphonate serves as a carboxyl-activating reagent to permit a direct preparation of versatile intermediate, 3-acyl-2-oxazolones or a one-step formation of amides from carboxylic acids.

Activation of carboxyl groups by diphenyl 2-oxo-3-oxazolinylphosphonate. Facile preparation of versatile reagents, 3-acyl-2-oxazolones

Abstract Synthetic utility of the 2-oxazolone moiety as an excellent new leaving group is described. Based on such a function of the heterocycles, diphenyl 2-oxo-3-oxazolinylphosphonate [DPPOx] has been newly introduced as a carboxyl-activating reagent which permits a facile direct preparation of 3-acyl-2-oxazolones and amides including peptides from a wide variety of carboxylic acids The 3-acyl-2-oxazolides also serve as versatile reactive agents for highly chemoselective acyl-transfer to the nucleophilic species such as amines, alcohols and thiols, providing convenient and high-yield routes to amides, esters and thiol esters under mild conditions. They are also useful intermediates for ketones and alcohols.

Highly selective acylation of amines and alcohols by poly(3-acyl-2-oxazolone)

Abstract Poly(3-acyl-2-oxazolone) serves as a convenient reagent for highly chemo- and regioselective acylation of polyamines, amino-alcohols and polyalcohols.

3-Acyl-2-oxazolone-zirconium complexes as excellent reagents for highly regioselective acylation of polyalcohols

Abstract In combination with 3-acyl-2-oxazolones, zirconium complexes such as zirconium acetylacetonate and zirconocene chloride hydride-Mg serve well as effective catalysts for regioselective acylation of polyalcohols including 1,2-diols to permit highly preferential protection of primary hydroxyl groups.

3-Acyl- and 3-alkoxycarbonyl-2-oxazolones and their homopolymers as amino-protecting reagents

Abstract 3-Acyl- and 3-alkoxycarbonyl-2-oxazolones as well as their homopolymers serve as practically useful N-protecting reagents of amines including α-amino acids.

Highly stereoselective photodimerization of 1,3-dimethylthymine in liquid crystalline media

Abstract Ordered media such as cholesteric and smectic solvents greatly enhance the stereoselectivity and the rate in photodimerization of 1,3-dimethylthymine, in contrast to the isotropic phase rections leading to a poor product-selectivity.

Stereo- and regio-selective formation of 2-oxazolone telomers as potential synthetic intermediates for aminosugars

Abstract 3-Acetyl-2-oxazolone readily undergoes free-radical homopolymerization as well as telomerization with polyhalomethanes, in which low telomer formation is highly stereo- and regio-selective.