Spectral features of laser induced plasma from YBa2Cu3O7 and GdBa2Cu3O7 highT c superconductors

Laser induced plasma emission spectra from highT _c superconducting samples of YBa₂Cu₃O₇ and GdBa₂Cu₃O₇ obtained with 1.06μm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides in addition to ionized species of the constituent metals in the plasma thus produced.     

Synthesis of cephalosporins carrying isoxazolyl acetamido and related side chains

Starting from 3,5-dimethylisoxazole the carboxylic acids I and V, the amino acids VIII (L-) and IX (D-), and the ureido acids X (L-) and XI (D-) were prepared, which were used for the synthesis of the new cephalosporins XVIIb, XXa-c (L-), and XXIb (D-). Thein vitro antibacterial activity of these semi-synthetic antibiotics was studied. The resorption of XVIIb was investigated in mice.Research Group for Antibiotics of the Hungarian Academy of Sciences, H-4010 Debrecen, P.O. Box 70, Hungary. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1524–1535, November, 1998.     

A novel and simple route for the synthesis of 3,4‐disubstituted pyrroles

A new class of 3,4‐disubstituted pyrroles has been prepared by the reaction of 1‐aroyl‐2‐arylsul‐fonylethenes and 1,2‐diarylsulfonylethenes with tosyl methyl isocyanide.     

2‐Pyrazolines from 1,3 ‐ dipolar cycloaddition of diazomethane to arylsulfonylethenes

Novel 2‐pyrazolines were obtained by the cycloaddition of diazomethane to bis(arylsulfonylethenyl)‐sulfones ( 3 ) and 1‐arylsulfonyl‐2‐styrylsulfonylethenes (7). Dehydrogenation of 2‐pyrazolines with chloranil gave pyrazoles.     

A Validated LC Method for Separation and Quantification of Voriconazole and Its Enantiomer

A simple liquid chromatographic method was developed for the separation and quantification of voriconazole and its enantiomer in drug substance. The separation was achieved on Chiral cel-OD (250 mm × 4.6 mm × 10 μm) using mobile phase consisting of n-hexane and ethanol in the ratio 9:1 (v/v) with a flow rate of 1.0 mL min⁻¹, at 27 °C column temperature and detection at 254 nm with an injection volume of 20 μL. Ethanol was used as diluent. The method is capable of detecting the (2S, 3R) enantiomer down to 0.0075% and can quantify down to 0.021% with respect to sample concentration. The method is rapid and the resolution achieved was about 3.0. This method can be employed for the quantification of (2S, 3R) enantiomer in voriconazole drug substance.     

Synthesis of cryptophycins via an N-acyl-beta-lactam macrolactonization

An efficient and concise approach to the synthesis of the macrolide core of the cryptophycins has been developed. A novel macrolactonization utilizing a reactive acyl-beta-lactam intermediate incorporates the beta-amino acid moiety within the 16-membered macrolide core. This modular approach, involving a cyanide-initiated acyl-beta-lactam ring opening followed by cyclization, was successfully applied to the total synthesis of cryptophycin-24. The strategy was also used in an efficient synthesis of the 6,6-dimethyl-substituted dechlorocryptophycin-52. In this case, the cyanide-initiated ring opening of the bis-substituted 2-azetidinone followed by macrolactonization was achieved through a catalytic process.     

Synthesis of thiadiazoles,triazoles and oxadiazoles from sulfonyl acetic acids via a common route

A new class of five membered heterocycles, thiadiazoles, triazoles and oxadiazoles were prepared from sulfonyl acetic acids via acid hydrazides.     

Palladium-catalyzed synthesis of carcinogenic polycyclic aromatic hydrocarbon epoxide-nucleoside adducts: the first amination of a chloro nucleoside

Pd-catalyzed coupling of the axially constrained, less reactive benzo[a]pyrene bay-region amino benzoates, derived from the tetrahydro and diol epoxides, with C-6 and C-2 halopurine deoxynucleosides offers an efficient approach to the synthesis of the corresponding nucleoside-epoxide adducts. Also reported are the first examples involving the coupling of a 6-chloropurine deoxynucleoside with these amines, a reaction that is difficult by direct halide displacement. Certain mechanistic aspects of this metal-catalyzed C-N bond formation are also discussed. [reaction--see text]