Cryomodification of drugs: Micronized amorphous state of carvedilol

By means of cryochemical modification, including substance evaporation in a stream of a heated gas-carrier with subsequent condensation of vapor on a surface, cooled up to the boiling temperature of liquid nitrogen (?196°C), the X-ray amorphous state of the drug carvedilol, (±)-1-(9H-carbazole-4-iloxy)-3-[2-(2-methoxyphenoxy)-ethylamino]propane-2-ol, was obtained. It is shown that, along with amorphization, cryomodification leads to micronization of the drug—the sizes of its particles decrease from an initial 5–10 up to 1–2 μm.     

Cryomodification of drugs: Micronization and crystalline structures of 1-(aminomethyl)-cyclohexaneacetic acid

Cryochemical modification is a method of micronization and changing of the crystalline structure of organic substances that in application with drug substances may lead to the improvement of their biopharmacological properties. This method was successfully developed for a chemically labile compound named gabapentin [1-(aminomethyl)-cyclohexaneacetic acid]. According to the data obtained by X-ray diffraction, FTIR spectroscopy, and differential scanning calorimetry (DSC), the formation of two kinetically stable polymorphic modifications of gabapentin (forms with melting points of 157°C and 163°C), which are different from the initial commercial one (with a melting point of 153°C) was observed. These two forms are well known, but the advantage of this work is in developing a new method of their production that excludes the use of any solvents, which is very important for environmental safety.     

Technetium(I) carbonyl dithiocarbamates and xanthates

Technetium(I) tetracarbonyl complexes with diethyldithiocarbamate and methylxanthate ligands [TcL(CO)(4)] (L = S(2)CNEt(2) and S(2)COMe) were prepared. Conditions required for the formation of these complexes were found. The crystal and molecular structure of the xanthate complex was determined by single-crystal X-ray diffraction. [Tc(S(2)CNEt(2))(CO)(4)] undergoes decarbonylation both in solution and in the course of vacuum sublimation with the formation of a dimer [Tc(S(2)CNEt(2))(CO)(3)](2) whose structure was determined by single-crystal X-ray diffraction. In donor solvents, [Tc(S(2)CNEt(2))(CO)(4)] and [Tc(S(2)COMe)(CO)(4)] undergo decarbonylation with the formation of tricarbonyl solvates [TcL(CO)(3)(Sol)]. The crystal structure of the pyridine solvate [Tc(S(2)CNEt(2))(CO)(3)(py)], chosen as an example, was determined by single-crystal X-ray diffraction. The possibility of using bidentate S-donor acidic ligands for tethering the tetracarbonyltechnetium fragment to biomolecules was examined.     

Synthesis and conversions of 2-substituted cinchoninic acid amides

Amides of 2-oxo- or 2-thiocinchoninic acid have been obtained by the reaction of substituted amides of 2-chlorocinchoninic acid with sodium acetate or sodium sulfide. The reaction of 2-thiocinchoninic acid amides with hydrazine hydrate or ethyl cyanoacetate leads to derivatives of 2-hydrazinocinchoninic acid or (4-carbamoyl-2-quinolyl)cyanoacetic ester respectively, which were also obtained from 2-chlorocinchoninic acid amides.Perm Pharmaceutical Academy, Perm 614600. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 697–700, May, 1997.     

Complexation of Nitroxide Radicals with Cyclodextrins: Kinetics of Crystal Complex Formation

Using the ESR method in combination with the stop-flow technique the kinetics of crystal complex formation of hydrophobic nitroxide radicals with cyclodextrins has been studied upon mixing cyclodextrin aqueous solutions with nitroxides emulsified in aqueous milieu. The - and -cyclodextrins and the piperidine nitroxide radicals with a OC(O)C_mH_2m+i (m = 7, 10, and 17) substituent in a para-position were used. It was established that the complexation process in the system emulsion of probe–cyclodextrin solution consists of two mainstages. The first stage is the transfer of probes from drops into aqueous solution and the formation of complexes RC_n, where R is the probe, C is cyclodextrin, n = 1, 2 and 3. The second stage is crystal complex formation and growth from solution of RC_n complexes. The results obtained indicate that mainly RC₃ complexes take part in crystallization. It was observed that the characteristic time of crystallization is approximately inversely proportional to the concentration of RC₃ complexes.Equilibrium constants of the processes R + C RC, RC + C RC₂ have been determined. It was found that complexation and further crystallization lead to the formation of monodispersed microcrystals.     

Elementary equivalence of endomorphism rings of Abelian p-groups

In this paper we study a relationship between elementary equivalence of endomorphism rings of Abelian p-groups and second-order equivalence of the corresponding Abelian p-groups. __________ Translated from Fundamentalnaya i Prikladnaya Matematika (Fundamental and Applied Mathematics), Vol. 10, No. 2, pp. 135–224, 2004.     

Modules

A survey is given of results on modules over rings, covering 1976–1980 and continuing the series of surveys “Modules” in Itogi Nauki.