Condensed pyridazines. Part IV. Reductive cyclization of (Z)-methyl 3-(6-azido-3-chloro-1-methyl-4-oxo-1,4-dihydropyridazin-5-yl)-2-rnethylacrylatc (I) to pyrido[2,3-c] pyridazines and the acid-catalysed cyclization of I to a pyrano[2,3-d] pyridazine

Reduction followed by cyclization of (Z)-methyl 3-(6-azido-3-chloro-1-methyl-4-oxo-1,4-dihydropyridazin-5-yl)-2-methylacrylate (I) to pyrido[2,3-c]pyridazines by treatment with triethyl phosphite or hydrazine hydrate as the reducing agents is described. Compound I was also reductively cyclized with sodium borohydride. Treatment of I with concentrated sulfuric acid gave 8-chloro-3,6-dimethyl-2,5-dioxo-5,6-dihydro-2H-pyrano[2,3-d] pyridazine (VII) which also could be synthesized by another independent route. A mechanism for the cyclization is proposed.     

Determination of monovalent inorganic anions in high-ionic-strength samples by electrostatic ion chromatography with suppressed conductometric detection

A new ion chromatographic (IC) system has been established by using micelles of 3-(N,N-dimethylmyristylammonio)propanesulfonate (Zwittergent 3-14) loaded onto a reversed-phase packed column as the separation column with an electronic rotary switching valve packed-bed suppressor for conductometric detection of inorganic anions. An aqueous H3BO3-Na2B4O7 solution has been demonstrated to be the most desirable eluent for this IC system. The relationship between retention time and the concentration of the borate eluent was determined for a series of model anionic analytes and this relationship was found to be opposite to that exhibited in a conventional anion-exchange IC system. The rapid elution and complete separation of monovalent inorganic anions were obtained by initially using a high-concentration borate solution as the eluent for a short-period, and then switching to a lower-concentration borate eluent to complete the separation. Detection limits for nitrite, bromide, nitrate, and chlorate were 0.85, 0.88, 0.95 and 4.8 microM, respectively, when a 7.0 mM Na2B4O7 eluent was used. Moreover, the ability to directly detect these monovalent anions in samples containing high concentrations of sulfate and/or chloride ions provided a major advantage of this approach.     

Synthesis and alpha-glucosidase-inhibiting activity of a new alpha-glucosidase inhibitor, 4-O-alpha-D-glucopyranosylmoranoline and its N-substituted derivatives

Various N-substituted derivatives of 4-O-alpha-D-glucopyranosylmoranoline have been synthesized, and their inhibitory activities against rabbit sucrase and maltase have been measured, as well as their effects on postprandial hyperglycemia in the sucrose-loaded rat, 4-O-alpha-D-Glucopyranosylmoranoline was also shown to have potent hypoglycemic activity in starch-loaded dogs.     

Improved spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol in the presence of benzyldimethylstearyltrimethylammonium chloride

An improved spectrophotometric determination of uranium(VI) is proposed using 4-(2-pyridylazo)resorcinol(PAR) in the presence of benzyldimethylstearyltrimethylammonium chloride(BSTAC) as a cationic surfactant. The calibration graph is linear in the range of 0.3-60 microg/10 ml uranium(VI), measuring the absorbance at 550 nm. The reproducibility for 19.0 microg/10 ml uranium(VI) is 0.57%. The third-derivative method using the third-derivative distance (d(3)A/dlambda(3)) among lambda(1) 530 nm, lambda(3) 594 nm and lambda(2) 565 nm was also investigated.     

Improvement of chemical analysis of antibiotics. IX. A simple method for residual tetracyclines analysis in honey using a tandem cartridge clean-up system

A simple, rapid and precise analytical method for the residual tetracyclines in honey has been established using a tandem cartridge clean-up system (prepacked reversed-phase and ion-exchange cartridges) followed by high-performance liquid chromatography. The recoveries of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC) and doxycycline (DC) from honey spiked at a level of 1.0 ppm are 87.1, 85.3, 98.0 and 99.0%, respectively, with coefficients of variation of 1.1-3.9%. The detection limits in honey are 0.02 ppm for OTC and TC, and 0.05 ppm for CTC and DC, respectively. The time required for the analysis of four samples is only 1 h.     

Synthesis and absolute configuration of +-lineatin,the pheromone of trypodendronlineatum

A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.0^4,7] nonane, $\text{1}$) was achieved. The stereochemistry of (+)-lineatin was established as 1$\text{R}$, 4$\text{S}$, 5$\text{R}$, 7$\text{R}$ by an X-ray crystallographic analysis of an intermediate $\text{1}$$\text{5}$.     

Semi-micro size-exclusion chromatography of polymers : Calibration of columns and comparison with conventional columns

Stainless-steel tubes having inside diameters of 1.5 mm and 1.8 mm were packed with polystyrene gels of particle diameter 10 ± 2 μm. Two 50 cm × 1.8 mm I.D. packed columns, connected in series, were calibrated and molecular-weight averages of polystyrene NBS 706 were measured, the results coinciding with the data of the National Bureau of Standards. The peak widths of polystyrenes of narrow molecular-weight distributions in both semi-micro column (four 25 cm × 1.5 mm I.D.) and conventional column (two 50 cm × 8 mm I.D.; packed by the manufacturer) systems were determined at different mobile-phase velocities, and the minimum peak width in the latter system was obtained at the velocity of 0.2 mm/sec, which was higher than that for the semi-micro system. The interstitial volume was higher and the inner volume was lower for the semi-micro column system (1.8 mm I.D.) than those for the conventional one, which means that semi-micro columns were packed less densely, resulting in a steep calibration curve. The peak height of a solute was proportional to the cell length of an ultraviolet detector if the sample load was proportional to the cross-sectional areas of columns having the same column efficiency. Although conventional size-exclusion chromatography has many advantages in respect of velocity, calibration curtve and sample peak height, semi-micro size-exclusion chromatography still holds some merits such as low consumption of gels and of mobile-phase solvents.