In-house reference materials of mometasone furoate with traceable assay certified values

Characterization of in-house reference materials (IHRMs) with traceable property values for the mometasone furoate assay is discussed. The traceability of the value carried by the IHRM has been established to the value carried by a higher metrological status United States Pharmacopoeia Reference Standard (USP RS). A comparative approach is used to overcome systematic errors in measurement results, specific to the measurement method and/or to the laboratory developing the IHRM. The traceability chain was realized by the simultaneous analysis of the IHRM and the USP RS test portions under the same conditions.     

DLTS and PTIS of new donors in oxygen-doped germanium

Two new DLTS bands I and II have been observed in n-type germanium containing 10¹⁶ cm^-3 interstitial oxygen. The signature of II is: E_c?E_II = 0.031 eV, K = 4 × 10⁷ cm^?2s^?1; level I is about half as deep. In addision, the excitation spectrum of I is recorded by PTIS. It is composed of three hydrogenic donor series Ia, b, c with activation energies 17.25, 17.6 and 18.1 meV. The donors I and II are thought to correspond with the well known thermal oxygen donors. Energies for the latter were determined at 0.017 and 0.04 eV from Hall effect by Fuller and Doleiden. The possibility of double donors is examined, in analogy with the case of oxygen donors in silicon.     

Study of the Synthesis of Dextran Derivatives

Abstract

The synthesis of biologically active high-molecular compounds offers an interesting subject for study in polymer chemistry. Dextran, one of the best blood plasma expanders, is a good product for use in synthesizing biologically active water-soluble polymers. This paper discusses the synthesis of water-soluble derivatives of dextran which can be used as drug carriers or as independent physiologically active compounds. The synthesis of these derivatives involved oxidation of dextran, O-alkylation of dextran, subsequent transformation of ethers of dextran containing reactive functional groups, and graft polymerization. Periodate oxidation of dextran resulted in the production of a derivative of dextran containing aldehyde groups: dialdehydedextran. Subsequent oxidation of dialdehyde-dextran with sodium chlorite permitted the introduction of carboxyl groups into the macromolecule of dextran. In order to introduce sulfonic acid, phosphonic, mercapto, chlorhydrinic, cyano, and aromatic amino groups into the macromolecule of dextran, dextran was alkylated with various alkylating reagents. The synthesized products were sulfopropyl, phosphonomethyl, mercaptoethyl, 3-chloro-2-hydroxypropyl, cyanoethyl, and 2-(3′-amino-4′-methoxyphenyl)-sulfonylethyl ethers of dextran. Treatment of the 3-chloro-2-hydroxypropyl ether of dextran with ammonia, amines, and aliphatic and aromatic amino acids produced ethers of dextran containing primary, secondary, and tertiary amino groups and quaternary ammonium groups, as well as residual aliphatic and aromatic amino acids.

Cyanethyl ether of dextran was used to synthesize derivatives of dextran containing thioamide and hydrazidine groups.

Graft copolymers of dextran and polyacrylic acid and of dextran and poly-2-methyl-5-vinylpyridine were synthesized. Redox systems were utilized to initiate graft copolymerizatLon with tetravalent cerium compounds used as oxidants and pentavalent vanadium with dextran or 2-(3′-amino-4′-methoxyphenyl)-sulfonylethyl ether of dextran used as reductant. This method produced graft copolymers with short graft chains.

The availability of the above derivatives of dextran has permitted the linking of drugs to dextran by different types of chemical bonds.     

Crystal Structure and Molecular Modeling of 4,4′-Bi-4H-cyclopenta[def]phenanthrenylidene and Related Derivatives

The twisted pentafulvene, 4,4-bi-4H-cyclopenta[def]phenanthrylidene, does not undergo oxidative electrocyclization to a semibuckminsterfullerene under photo-oxidative conditions. However, the use of standard dehydrogenating agents such as DDQ or tetrachloro-2,3-benzoquinone at 200°C resulted in partial oxidative electrocyclization and formation of a Diels–Alder adduct, respectively. The crystal structure of this Diels-Alder adduct was obtained and shown to possess C₂ symmetry. The crystal structure for 4,4-bi-4H-cyclopenta[def]phenanthrylidene was also obtained and the molecular parameters differ slightly from what was previously reported for the same compound. Molecular modeling of this pentafulvene gave a twist angle matching the crystal structure. Similar modeling of related bifluorenylidene, bis-1,1-indenylidenes and biscyclopentadienylidene gave twist angles which correlate with the computed heats of hydrogenation for the bridging alkene unit.