No abstract

During mineral growth in rat bone-marrow stromal cell cultures, gallium follows calcium pathways. The dominant phase of the cell culture mineral constitutes the poorly crystalline hydroxyapatite (HAP). This model system mimics bone mineralization in vivo. The structural characterization of the Ga environment was performed by X-ray absorption spectroscopy at the Ga K-edge. These data were compared with Ga-doped synthetic compounds (poorly crystalline hydroxyapatite, amorphous calcium phosphate and brushite) and with strontium-treated bone tissue, obtained from the same culture model. It was found that Sr(2+) substitutes for Ca(2+) in the HAP crystal lattice. In contrast, the replacement by Ga(3+) yielded a much more disordered local environment of the probe atom in all investigated cell culture samples. The coordination of Ga ions in the cell culture minerals was similar to that of Ga(3+), substituted for Ca(2+), in the Ga-doped synthetic brushite (Ga-DCPD). The Ga atoms in the Ga-DCPD were coordinated by four oxygen atoms (1.90 A) of the four phosphate groups and two oxygen atoms at 2.02 A. Interestingly, the local environment of Ga in the cell culture minerals was not dependent on the onset of Ga treatment, the Ga concentration in the medium or the age of the mineral. Thus, it was concluded that Ga ions were incorporated into the precursor phase to the HAP mineral. Substitution for Ca(2+ )with Ga(3+) distorted locally this brushite-like environment, which prevented the transformation of the initially deposited phase into the poorly crystalline HAP.

Several 3-Ω-amino monosubstituted hydantoins have been obtained in the reaction of isocyanate of glycine ethyl ester with the appropriate aliphatic or aromatic diamine. It was found, that the 3-(aminoaryl) monosubstituted hydantoins may be diazotized and their diazonium salts may be coupled and hydrolysed without changes in the hydantoin ring. [6]. 3-Monosubstituted hydantoins with the free amine group with the substituent at the 3 position are even more scarce and their syntheses have low yield [7] or is protected by patents [8,9].Results and Discussion.In this paper 3-monosubstituted amino and dialkylamino alkyl and aryl hydantoins were synthesized according to the known method [10] and its applications [11]. It involves the reaction between the appropriate diamine and the isocyanate of glycine ethyl ester (Scheme 1). The reaction was carried out at room temperature or alternatively at 0°C. Chloroform or anhydrous ethanol was used as solvents due to the solubility of the substrates. After the reaction, the unisolated intermediate, i.e., a derivative of ethyl ester of hydantoic acid, was cyclised under acidic (HCl) conditions to the appropriate hydantoin in water-e t h a n o l solution. The raw product obtained was purified as a hydrochloride or, after transformation, as a free base. For the synthesis of derivatives with a free amino group a monoacetyl derivative of the diamine was used as substrate. It was found that when a monoalkyldiamine, i . e. N-methyl-1,3-propanediamine, was used the reaction did not follow the proposed scheme (Scheme 1). Immediately after mixing of reagents a mixture of various products was obtained, evidenced by monitoring the reaction in CDCl 3 solution by 1 H NMR spectroscopy. After careful evaporation of the solvent and drying under reduced pressure at 40°C the intermediate was hydrolysed in HCl medium. A mixture of different products was obtained and among them c a. 10% of N-methyl-1,3-propanediamine hydrochloride, the presence of which (confirmed by 1 H NMR, 13 C NMR and MS) may mean that during the mentioned reaction a partial amidation of the ester group of the isocyanate occured. To obtain the indole derivative of 3-monosubstituted hydantoin, 5-aminoindole and isocyanate of glycine ethyl ester were used (Scheme 1). The indole derivative of the ester of hydantoic acid 9 w a s obtained with satisfactory yield but attempts to cyclise it to the hydantoin derivative proved unsuccessful although HCl, CH 3 COOH and heating without a solvent were tried. In each case the final result was a mixture of diff e r e n t , unidentified substances.One of the major aims of this work was to determine whether the free amine group in the 3-monoaminoaryl substituent reacts without simultaneous changes in the hydantoin ring. The reactions were carried out with 3-(4'-aminophenyl)hydantoin 8, which was transformed in the non-isolated diazonium salt (8a) (Scheme 2) at 0 °C without a change of the NH group of the hydantoin ring in the nitroso group [12]. This salt was remarkably stable and could be heat...

Durch Kondensation von Isothioeyunuten (I) mit Aminosiiiiren (II) werden Thiohydantoine (III) erhalten.

In the reaction of ethyl isothiocyanatoacetate with diamines, followed by cyclization of the intermediate product, 3-monosubstituted thiohydantoins have been obtained. It was found that the reaction course depends on the purity of the isothiocyanate used and also, in the case of dialkylaminoamines, the selfcyclization occurs. Besides the dialkylamino derivatives of 3-monosubstituted 2-thiohydantoins also new monoalkylamino, amino and heterocyclic derivatives were synthesized. The aryldiazonium derivative of 3-monosubstituted 2-thiohydantoin yielded both respective phenol derivative after hydrolysis and the product of coupling with 2-naphthol.J. Heterocyclic Chem., 40, 665(2003).2-Thiohydantoins, in common with their 2-oxo analogs, have interesting pharmacological activity [1-3], technical applications [4,5] and properties [6,7]. Investigations on these compounds is less active in comparison to hydantoins due to their difficult synthesis and higher toxicity. A relatively small number of 3-monosubstituted 2-thiohydantoins have been synthesized to date, and only a few among them possess dialkylamino substituents [8][9][10]. 2-Thiohydantoins with amino or hydroxy group in the substituent in 3 position are not reported in the literature. This is due mainly to diff iculty of synthesis, because it is impossible to obtain aliphatic or aromatic isothiocyanates with a free amino group, as well as aliphatic ones with hydroxy group. Such isothiocyanates are pre-requisite in the standard synthesis [ 11] of 3-monosubstituted 2-thiohydantoins.Results and Discussion.The dialkylamino, amino and hydroxy derivatives of 3-monosubstituted 2-thiohydantoin described in this paper were obtained by the literature method [12] using ethyl isothiocyanatoacetate and respective diamine, aminoalcohol or aminophenol. Mass spectrometry investigations showed that the starting isothiocyanate contains small amounts of thiophosgene and carbon disulfide. These contaminants could not be removed from the reagent obtained according to literature [13] by standard procedures like vacuum distillation (an azeotrope was formed).It was found that these minor contaminants markedly influence the reaction, yielding tar-like products of unidentified composition. Using highly pure isothiocyanate, obtained by removal of contaminants by purging with