[Study of conformation structure and molecular interactions of rosamycin by infrared spectrum analysis]. / Issledovanie konformatsionnoi struktury i molekuliarnykn vzaimodeistvii rozamitsina po IK-spektram.

IR spectra of rosamycin and its solutions in inert (CCl4 and C2Cl4), proton acceptor (tetrahydrofuran, hexametapol and diethylamine) and proton donor (CHCl3 and CH3OD) solvents were studied at various concentrations (0.1 to 0.001 mol/l) and temperatures (20 to 100 degrees C) in the region of the vC = O and vOH absorption bands (1600-1800 and 3200 3650 sm 1). It was found that the absorption bands at 3480 and 3560 sm-1 observed in the spectra of rosamycin diluted solutions in the inert solvents referred to variations of vOH...N of the aminosugar fragment and to vOH...O = C of the ester group of the macrocycle. Bands at 1697 and 1717 sm-1 referred to vC = O of the ketone and aldehyde carbonyl groups and band at 1728 sm-1 referred to vC = O of the ester group whose carbonyl was involved in the C = H...HO intramolecular hydrogen bond. Intensity of vC = O band (1745 sm-1) of the free ester group was nought. However, it increased with using the proton acceptor solvents. OH...N and OH...O = C intramolecular hydrogen bonds stabilized rosamycin molecule conformation. Mechanism of rosamycin interaction with the proton donor and acceptor molecules was elucidated. It was shown that tertiary nitrogen was the center of rosamycin molecule protonation.

[IR spectral research on erythromycin mono- and dihydrates]. / Issledovanie mono- i digidrata éritromitsina po IK-spektram.

The IR spectra of crystalline and amorphous forms of erythromycin monohydrate and dihydrate were investigated and their characteristic spectral features were described. Differences in the system of the intermolecular hydrogen bonds and in the level of perfection of the crystalline structures of the monohydrate and dihydrate were detected. It was shown that both crystallohydrates of erythromycin might exist in two polymorphous modifications. The crystalline structure of the low temperature modification of the monohydrate was of low perfection. At 75-80 degrees C irreversible polymorphous conversion of erythromycin monohydrate and erythromycin dihydrate accompanied by changes in the hydration water state was observed. The crystalline structures of high temperature modifications of the erythromycin crystallohydrates were identical.

[Infrared spectra and the molecular conformations of macrolide-group antibiotics in solution]. / Infrakrasnye spektry i knoformatsii molekul nekotorykh antibiotikov gruppy makrolidov v rastvore.

IR spectra (1,600-1,800, 3,100-3,700 cm-1) of tetrachlorethylene solutions of macrolide antibiotics such as erythromycin monohydrate and dihydrate, oleandomycin, erythrolose amine and anhydroerythromycin were obtained. The atoms and atomic groups included into the hydrogen bond were determined. It was shown that the antibiotic molecule conformations were stabilized by the intramolecular hydrogen bonds.

[Hydrogen bond and acid-base interactions in erythromycin solutions]. / Vodorodnaia sviaz' i kislotno-osnovnye vzaimodeistviia v rastvorakh éritromitsina.

The association and conformational structure of the molecule of erythromycin in solutions of CCl4, C2Cl4 and CHCl3 were studied by the IR spectra in the region of v OH and vC = O. The analysis of the concentration and temperature changes showed that the erythromycin association was accounted for by the hydrogen linkage of OH ... O = C to the ester group. In the monomer molecule of erythromycin, all hydroxyl groups participated in the intramolecular hydrogen linkage. Band 3513 cm-1 belonged to the OH group in the five-membered cycles of OH ... O. Components 3500, 3530 and 3560 cm-1 of the wide band vOH were assigned to the cycles with OH ... N and OH ... O linkages of a larger size. The association was due to a break in a part of the intramolecular hydrogen linkages. Addition of strong acceptors of proton-hexamethanol and trioctylphosphinoxide to the solution resulted in attenuation of these bands and appearance of a strong band vOH of the erythromycin-acceptor complexes. In the presence of monochloroacetic acid in the solution of CHCl3 stoichiometric protonization of erythromycin was observed. The total acid was in the form of anion (vaCO-2 1610 cm-1) up to a ratio of 1:1. The protonization proceeded according to the nitrogen atom since the antibiotic spectrum in the region of vC=O did not change. Propionic acid titrated erythromycin in methanol solution and in mixtures of water and methanol up to a ratio of 1:5 (v/v). However, in the solution of CHCl3 equilibrium between the neutral and ionized molecules of the acid was seen.