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Tetrabutylammonium triphenydifluorosilicate (TBAT) has been found to be a useful reagent for the conversion of 6-chloropurine nucleosides to 6-fluoropurine derivatives. The 6-chloropurine nucleosides were reacted with trimethylamine to form quaternary trimethylammonium salts which were treated in situ with TBAT in DMF to effect conversion to the 6-fluoro derivatives in yields of 59–72%.

Protected L-phenylalanine was reduced to L-1,4-cyclohexadienylalanine followed by ozonolysis of the unsaturated ring. Intramolecular cyclization of the ozonolysis product occured upon treatment with acid. The cyclization of the product of ozonolysis with hydroxylamine was studied as well. The formation of both 5- and 3-isoxazolylalanine is demonstrated. Mechanism of formation of these products and structure of intermediates are discussed.

Optically active derivatives of L-isoxazolo[2,3-a ]pyrimidin-4-ylalanine are prepared by the combination of Birch reduction of the phenyl ring of L-phenylalanine, followed by ozonolysis and condensation with 3-amino-5-oxo-4-phenyl-2,5-dihydroisoxazole. Ring cleavage of the five-membered ring by reduction, oxidation and nucleophiles gives pyrimidylalanine derivatives.

Derivatives of 2-(1,4-cyclohexadienyl)glycine were subjected to total ozonolysis. The free esters as well as the N-protected esters tend to cyclize to yield 2-carbethoxy-3-hydroxy pyrrole derivatives. By treatment of the ozonolysis mixture with hydroxylamine or phenylhydrazine heterocyclic derivatives of glycine were obtained. The structure and formation of pyrazolyl and isoxazolyl glycine derivatives is discussed. The structure of N-acetyl-2-(1-phenylpyrazol-3-yl)glycine ethyl ester by X-ray single crystal analysis is reported.

The reaction of 4-phenyl-3,5-dihydroxyisoxazole with α,β-unsaturated cyclic ketones and 1,3-cyclic diketones was studied. β-Substituted α,β-unsaturated ketones give pairs of isomeric isoxazolium enolates. The remarkable influence of the heterocyclic betaine on the proton chemical shifts is discussed. 1,3-Cyclic diketones reacted spontaneously with 4-phenyl-3,5-dihydroxyisoxazole yielding isoxazolium enolate enols and enol ethers.

The aromatic ring in L-phenylalanine was transformed into isoxazolyl, N-phenylpyrazolyl, and the bicyclic pyrazolo[1,5-a]pyrimidinyl groups, by a combination of Birch reduction and ozonolysis, followed by condensation with the relevant binucleophiles. The ozonolysis was carried out on the N-acylated esters of cyclohexa-1,4-dienylalanine. The resulting N-acylated esters of heterocyclic alanine derivatives were obtained without isolation of the ozonolysis products. 4-Phenylpyrazolidine-3,5-dione was used as a ‘hydrazine donor’ in the construction of a pyrazolyl group, as direct condensation with hydrazine was successful.

Optically active derivatives of L-isoxazolo[2,3-a ]pyrimidin-4-ylalanine are prepared by the combination of Birch reduction of the phenyl ring of L-phenylalanine, followed by ozonolysis and condensation with 3-amino-5-oxo-4-phenyl-2,5-dihydroisoxazole. Ring cleavage of the five-membered ring by reduction, oxidation and nucleophiles gives pyrimidylalanine derivatives.

Protected L-phenylalanine was reduced to L-1,4-cyclohexadienylalanine followed by ozonolysis of the unsaturated ring. Intramolecular cyclization of the ozonolysis product occured upon treatment with acid. The cyclization of the product of ozonolysis with hydroxylamine was studied as well. The formation of both 5- and 3-isoxazolylalanine is demonstrated. Mechanism of formation of these products and structure of intermediates are discussed.

Tetrabutylammonium triphenydifluorosilicate (TBAT) has been found to be a useful reagent for the conversion of 6-chloropurine nucleosides to 6-fluoropurine derivatives. The 6-chloropurine nucleosides were reacted with trimethylamine to form quaternary trimethylammonium salts which were treated in situ with TBAT in DMF to effect conversion to the 6-fluoro derivatives in yields of 59–72%.

The aromatic ring in L-phenylalanine was transformed into isoxazolyl, N-phenylpyrazolyl, and the bicyclic pyrazolo[1,5-a]pyrimidinyl groups, by a combination of Birch reduction and ozonolysis, followed by condensation with the relevant binucleophiles. The ozonolysis was carried out on the N-acylated esters of cyclohexa-1,4-dienylalanine. The resulting N-acylated esters of heterocyclic alanine derivatives were obtained without isolation of the ozonolysis products. 4-Phenylpyrazolidine-3,5-dione was used as a ‘hydrazine donor’ in the construction of a pyrazolyl group, as direct condensation with hydrazine was successful.