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Enantiomers of 2-methyl-6-nitro-1,2,3,4-tetrahydroquinoline have been obtained by kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline in acylation with acyl chlorides of N-protected amino acids followed by regioselective nitration of the diastereoisomeric amides and acidic hydrolysis. The introduction of a trifluoroacetyl protecting group into the position 1 of the enantio pure nitro compound followed by the reduction led to (S)-6-amino-2-methyl-1-trifluoroacetyl-1,2,3,4-tetra-hydroquinoline in a high yield.

Acylative kinetic resolution of racemic amines occupies a highly important place among the methods for preparation of enantio enriched or pure amines. Nonenzymatic acylative kinetic resolution is usually carried out in the presence of chiral acyl-transfer catalysts or under the action of chiral enantio- or diastereoselective resolving agents. Recently, this line of investigations has been rapidly developed and very interesting results of design and synthetic application of both new catalysts and chiral acylating agents have been obtained. This microreview summarizes the recent advances in this area.

Kinetic resolution of racemic 3-methyl-2,3-dihydro-4H-[1,4]benzoxazines in the reaction with chiral 2-arylpropionyl chloride predominantly yielded R*,R*-diastereomers. Ibuprofen acyl chloride as acylating agent was found to be more selective and sensitive to the changes in the reaction temperature as compared to naproxen acyl chloride and 2-phenylpropionyl chloride.

The comparative X-ray diffraction study of racemic and (S)-enantiomer of 7,8-difluoro-3-methyl-2,3-dihydro-4H-[1,4]benzoxazine was carried out. The both forms of benzoxazine are crystallized in the orthorhombic crystal system, the (S)-enantiomer is crystallized in the chiral space group P212121, while the racemate is crystallized in the centrosymmetric Pbca space group. The bond lengths and bond and torsional angles in the both molecules are almost equal. The packing of the racemate is characterized by a closer interaction of polar NH…O groups.

The acylative kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2,3-dihydro-3-methyl-4H-1,4-benzoxazine using acyl chlorides of N-phthaloyl-(S)-phenylalanine, N-phthaloyl-3-(4-nitrophenyl)-(S)-alanine and N-phthaloyl-O-methyl-(S)-tyrosine as chiral resolving agents has been carried out. It is shown that the effectiveness of an acylative kinetic resolution depends on the electronic effects of substituents in the phenyl fragment of the acylating agent and increases as the electron-donating properties of the para-substituent (OMe > H > NO2) in phenyl fragment of N-phthaloyl-3-aryl-(S)-alanyl chlorides increase; conducting the process at a reduced temperature also contributes to an enhancement of the kinetic resolution.

A comparative study of the kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2,3-dihydro-3-methyl-4H-1,4-benzoxazine using N-phthaloyl-(S)-amino acyl chlorides as chiral acylating agents is described. Temperature and solvent effects on the stereochemical features have been examined. It has been found that N-phthaloyl-(S)-phenylalanyl and N-phthaloyl-(S)-2-phenylglycyl chlorides bearing aromatic substituents close to the stereogenic centre are more stereoselective acylating agents than N-phthaloyl-(S)-alanyl chloride. For the preparative kinetic resolution of racemic amines N-phthaloyl-(S)-phenylalanyl chloride proved to be the most appropriate chiral acylating agent.

New routes to closo-carboranyl derivatives of L-lysine and L-glutamic acid with free gA-NH2 groups were proposed.

Acylative kinetic resolution of racemic amines occupies a highly important place among the methods for preparation of enantio enriched or pure amines. Nonenzymatic acylative kinetic resolution is usually carried out in the presence of chiral acyl-transfer catalysts or under the action of chiral enantio- or diastereoselective resolving agents. Recently, this line of investigations has been rapidly developed and very interesting results of design and synthetic application of both new catalysts and chiral acylating agents have been obtained. This microreview summarizes the recent advances in this area.

Reaction of N2-protected 2-amino-6-chloropurine with tert-butyl (S)-phenylalaninate, (R)- and (S)-valinates followed by deprotection affords 2-aminopurines bearing at 6-position the corresponding amino acid moieties, whose chiral centre is partially racemized.