Facile and convenient method of deuterium gas generation using a Pd/C-catalyzed H2-D2 exchange reaction and its application to synthesis of deuterium-labeled compounds

The Pd/C-catalyzed H(2)-D(2) exchange reaction using a H(2)-D(2)O combination provided a general, efficient and environmentally friendly route for the preparation of deuterium gas (D(2)). H(2) sealed in a reaction flask was converted into nearly pure D(2), which could be used for the Pd/C-catalyzed one-pot reductive deuteration of various reducible functionalities and the chemoselective one-pot deuterogenation of olefin and acetylene. Additionally, we established the capturing method of the generated D(2) in a balloon, which was successfully applied to the Pd/C-catalyzed reductive mono-N-alkylation of a primary amine using nitrile as the alkylating reagent.     

An improved radiochemical procedure for low-level measurements of americium in environmental matrices

The chemical yield and accuracy of measurements of (241)Am at low levels in marine environmental matrices have been substantially improved by applying the extraction procedure with DDCP (dibutyl-N,N-diethylcarbamylphosphonate). The improved procedure is described, and its advantages over the conventional procedure are discussed.     

On-line determination of trace sulfur dioxide in air by integrated microchip coupled with fluorescence detection

A microchip-based method was developed for on-line determination of trace sulfur dioxide (SO₂) in air. Gaseous SO₂, which diffused through the porous glass materials on the microchip, was absorbed into an absorption solution of triethanolamine (TEA) as sulfite ions and reacted with N-(9-acridinyl)maleimide (NAM), which was used as a fluorescent reagent. The fluorescence of NAM-sulfite in micro-fluidic channel was detected. The calibration curve of sulfite ions in the range of 1.5-30 μmol/L (SO₂ 3-60 ppbv) showed a linear relation R² = 0.995, and the relative standard deviation (R.S.D.) was 1.9% for 10 μmol/L sulfite ions in five measurements. The entire measurement procedure was achieved by the integrated microchip, and the consumption of reagents was drastically reduced. It was satisfactory to apply this method to determine on-line the SO₂ level in the air.     

Nucleoside analogs. I. A synthesis of 1,3-dihydroxy-2-(6-substituted-9-purinyl)cyclohexane

Biologically active 1,3-dihydroxy-2-(6-substituted-9-purinyl)cyclohexanes (VI-X) were prepared by a reaction between trans-2-amino-1,3-cyclohexanediol (I) and 4,6-dichloro-5-amino-pyrimidine (II), followed by cyclization and nucleophilic substitution. Compounds VI and VII showed a weak inhibitory effect against Xanthomonas oryzae, a pathogenic bacteria of leaf blight of rice plant.     

Synthesis of 1,10-dimethylbicyclo[8.8.8]hexacosane and 1,10-dihydroxybicyclo[8.8.8]hexacosane

[structure: see text] 1,10-Dimethylbicyclo[8.8.8]hexacosane (1) and 1,10-dihydroxybicyclo[8.8.8]hexacosane (2) were prepared in 4% yield over seven steps and in 18% yield over three steps, respectively, starting from 1,10-cyclooctadecanedione. The identities and out,out conformations of these compounds were established by single-crystal X-ray analysis.     

General method of obtaining deuterium-labeled heterocyclic compounds using neutral D2O with heterogeneous Pd/C

A protocol of a versatile H-D exchange reaction of heterocyclic compounds catalyzed by heterogeneous Pd/C in D₂O is described. The reaction of various nitrogen-containing heterocycles with 10% Pd/C (10 wt % of the substrate) under hydrogen atmosphere in D₂O as a deuterium source at 110-180 °C for 24 h afforded the corresponding deuterated compounds with satisfactory efficiency of deuteration in moderate to excellent isolated yields. Furthermore, the Pd/C-H₂-D₂O system can be extended to the direct deuteration of biologically active compounds such as sulfamethazine, which is used as a synthetic antibacterial drug for fat stocks and would be applied as a general method for the preparation of the standard materials for the analysis of residual chemicals in foods and so on.     

High levels of cholesteryl esters, progesterone and estradiol in the testis of aging male Fischer 344 rats: feminizing Leydig cell tumors

The levels and fatty acid composition of cholesteryl esters (CEs), and the levels of steroid hormones in the testis of aging Fischer 344 (F344) rats were studied in comparison with those of 6-month-old rats without Leydig cell tumors (controls). The total lipid content in the testis increased as Leydig cell tumors developed: in 23-month-old rats, the content increased to five times higher than that of the controls. The CE level reached about 300 times higher than that of the controls and comprised 57.5% of the total lipid of the testis. The fatty acid composition of the CEs in the tumor compared to the normal tissue from the controls was characterized by a marked increase in 22:4 (n-6) and a decrease in 22:5 (n-6), a characteristic acid in rat testis lipids. Testicular progesterone levels considerably increased with the development of tumors (23-month-old rats, 2870 ng/wet wt; controls, 7 ng/g wet wt). Also, levels of estradiol showed striking increments (23-month-old rats, 2205 pg/g wet wt; controls, 153 pg/g wet wt). On the other hand, testosterone levels decreased (23-month-old rats, 13 ng/g wet wt; controls, 50 ng/g wet wt). These results suggest that Leydig cell tumors in aging F344 rats resemble the ovary tissue of rats in the levels and fatty acid composition of the CEs, and in the levels of steroid hormones. This is supported by the observation that the two kinds of cells found in the tumor tissue resemble cells of the corpus luteum and granulosa cells of the follicles, respectively, in the ovary of rats. In conclusion, the study shows that Leydig cell tumors in aging male F344 rats have a tendency towards feminization.