General meeting of the division of chemical sciences of the academy of sciences U.S.S.R. to celebrate the 75th birthday of academician A. E. Arbuzov

Russian Chemical Bulletin -     

Polysaccharides ofUngernia. VII. Partial hydrolysis of the mannan of the bulbs ofU. vvedenskyi

4-O--D-Manopyranosyl-D-mannose, O--D-mannopyranosyl-(l4)-O--D-mannopyranosyl-(14)-D-mannose, and 0--D-mannopyranosyl-(14)-O--D-mannopyranosyl-(l4)-O--D-mannopyranosyl-(l4)-D-mannose have been isolated fron the products of the partial hydrolysis of ungeromannan-V, obtained fron the bulbs ofUngernia vvedneskyi, and have been identified. This set of oligosaccharides confirms the regular structure of the carbohydrate chain of ungeromannan-V, which consists of a linear sequence of -14-bound D-mannose residues.DeceasedTranslated from Khimiya Prirodnykh Soedineii, No. 4, pp. 434–436, July–August, 1981.     

Analysis of the equations for the temperature dependence of the retention index. I. Relation between equations.

The relation between the parameters of several equations for the retention index temperature dependence was established, taking the hyperbola deduced from the retention theory as starting point. The transformation factors depend only on methylene contributions to the thermodynamic functions of solution and temperature. Their evolution with the mean temperature of the range was illustrated for SE-30 and Carbowax-20M glass capillary columns. On this basis the post-run standardisation of dI/dT values at a reference mean temperature is possible. Examples and statistical correlation between series of parameters from different equations for perfumery solutes were shown.     

Polysaccharides ofUngernia. XIII. Carbohydrates of the leaves of the genusUngernia

The present communication gives the results of an investigation of the carbohydrates isolated from the leaves of eight species ofUngernia. From a single sample were successively extracted the water-soluble polysaccharides, the glucofructans, the pectin substances, and the hemicelluloses. The qualitative and quantitative monosaccharide compositions of the carbohydrates isolated were determined, and the characteristics of the pectin substances are given.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 647–650, September–October, 1984.     

On the birthday of R. M.-F. Salikhdzhanova

Chronicle

On the birthday of R. M.-F. Salikhdzhanova     

Chemistry of the diazeniumdiolates. 3. Photoreactivity

We have found O(2)-substituted diazeniumdiolates, compounds of structure R(2)N-N(O)=NOR' that are under development for various possible pharmaceutical uses, to be rather photosensitive. With R = ethyl and R' = methyl, benzyl, or 2-nitrobenzyl, the observed product distributions suggest that two primary pathways are operative. A minor pathway involves the extrusion of nitrous oxide (N(2)O) with simultaneous generation of R(2)N(*) and R'O(*), which may then form amines, aldehydes, and alcohols. The major reaction pathway is an interesting photochemical cleavage of the N=N bond to form a nitrosamine (R(2)NN=O) and an oxygen-substituted nitrene (R'ON). The intermediacy of the O-nitrene was inferred from the production of abundant oxime, via rearrangement of the O-nitrene to a C-nitroso compound (R'ON --> O=NR'), and subsequent tautomerization to the more stable oxime. Involvement of the O-nitrene was confirmed by trapping with 2,3-dimethyl-2-butene to form the aziridine and with oxygen to generate the nitrate ester. 2-Nitro substitution on the benzyl derivative had surprisingly little effect on the reaction course. For each compound examined, minor amounts of nitric oxide (NO), presumably produced by secondary photolysis of the nitrosamine, were observed. Time-resolved infrared experiments provided additional support for the above reaction pathways and confirmed that the nitrosamine is a primary photoproduct. We have also found that the relative contributions of the reaction pathways can be altered in certain derivatives. For example, when R' = 2,4-dinitrophenyl, the contribution of the nitrosamine/O-nitrene-forming pathway was diminished. Pharmacological implications of these results are discussed.     

On the Use of the Knox Equation. I. the Fit Problem

Abstract

To obtain significant A, B, and C parameters of the Knox equation, which corresponds to the plot of the reduced plate height, h, versus the reduced linear velocity, v, actual results must be fitted correctly. The Knox equation is analyzed, the rôle of each individual parameter is shown. The equation producing the coordinates of the minimum plate height (maximum efficiency) is fully derived from the derivative of the Knox equation. Two tables giving the minimum coordinates for usual A, B, and C ranges are listed. The classical fit method is derived and analyzed. A graphical fit method which uses the remarkable graphical capabilities of modern spreadsheet packages is described. A synthetical set of data was fitted. It is demonstrated that each Knox parameter, obtained through fit procedures, must be given with the fitting confidence interval which is often in the 20% range.     

Improvements in the thin-layer chromatography of natural products. I. Thin-layer chromatography of the aflatoxins.

During the period which has elapsed since the aflatoxins were first isolated, one of the main problems has been the separation of the individual aflatoxins in pure form from aflatoxin-containing extracts. This separation has been best effected by thin-layer chromatography, and in this paper we describe how some of the difficulties may be overcome by using an appropriate combination of solvent system and silica gel preparation. For the examination of aflatoxin-containing extracts from the mycelia of Aspergillus flavus moulds, an initial freeze-drying step has been found to improve appreciably the quality of the chromatograms obtained.