N-(2-(2-pyridyl)ethyl)chitosan: Synthesis, characterization and sorption properties.

The method of producing N-2-(2-pyridyl)ethylchitosan (PE-chitosan) with substitution degrees (DS) up to 1.2 has been developed using the "synthesis in gel" approach for direct addition reaction between 2-vynilpyridine and chitosan. Investigation of sorption properties has revealed significantly higher affinity of pyridylethyl fragments to Pt(IV)) and Pd(II) ions compared to the unsubstituted amino groups of chitosan. The maximum sorption capacities of PE-chitosan in 0.1M HCl solution were estimated as 5.56mmol/g for Au(III), 3.67mmol/g for Pd(II), and 2.75mmol/g for Pt(IV). Sorption capacities of PE-chitosan for transition metal ions at pH 4-8 were 1.5-2.6 higher than those of chitosan with the highest values attained for Cu(II) and Ag(I) ions - 1.50mmol/g and 1.53mmol/g, respectively. The PE-chitosan application for preconcentration of Au(III) with subsequent elution with HCl/thiourea mixtures was proved to be efficient for atomic absorption spectroscopy analysis of multi-component solutions with low gold content.

[A novel laboratory method of isolation and purification of tobramycin]. / Razrabotka novogo laboratornogo metoda vydeleniia i ochistki tobramitsina.

A new laboratory method for isolation and purification of tobramycin by using extraction of a tobramycin derivative with benzaldehyde by methylene chloride, subsequent hydrolysis of azomethine and recrystallization of the formed tobramycin sulfate from solution of sulfuric acid in methanol was developed. The method allows to exclude the stage of chromatographic purification of tobramycin, to reduce the time of the process realization from 120-125 h to 15-20 h, to increase the yield of the target product from 37-40% to 60-65% without decreasing the product quality, to exclude a number of large-size and expensive equipment and to ensure high reproducibility of the technology.

Synthesis of ( 2S, 4S)-4-phenylamino-5-oxoproline derivatives.

The paper describes the synthesis of ( 2S, 4S)-4-(N-Ts)- and ( 2S, 4S)-4-(N-Boc)-phenylamino-5-oxoprolines (pyroglutamic acid). These derivatives have been shown to be useful for synthesis of their amides and peptides in spite of steric hindrances caused by bulky groups adjacent to the reaction centre. Under the conditions applied no lactam ring opening and no loss of stereochemical integrity of any of the chiral centres were observed, which has been confirmed by NMR techniques.