Gas-liquid chromatography-mass spectrometry of acetates of partially methylated methyl glycosides. VII. Mono- and dimethylheptoses

The partial methylation of methyl β-glucoheptopyranoside has given a complex mixture of methyl ethers, from which five monomethyl ethers have been isolated by preparative GLC. Methylation of the latter gave a mixture in which ten dimethyl ethers were detected. The retention indices on the phase NPGS of the mono- and dimethyl ethers of methyl β-glucoheptopyranoside have been measured, and their mass spectra have been recorded and discussed. The mass spectra of these position isomers unambiguously characterize the pattern of methylation.     

Gas-liquid chromatography-mass spectrometry of acetates of partially methylated methyl glycosides. VII. Tri- and tetramethylheptoses

Nine tri- and five tetramethyl ethers have been obtained by the partial methylation of methyl - and -glucoheptopyranosides and methyl 2,3,4,6,7-penta-O-acetyl1-- and--glucoheptopyranosides. The retention indices of both types of methyl ethers on the liquid phase NPGS have been measured and the main directions of the fragmentation of these compounds under electron impact have been determined. The laws of the mass spectra of the position isomers that have been found will permit their use in GLC-MS analysis for determining the structure of a polysaccharide by the methylation method.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 492–498, July–August, 1982.     

Gas-liquid chromatography-mass spectrometry of acetates of partially methylated methyl glycosides. VII. Tri- and tetramethylheptoses

Nine tri- and five tetramethyl ethers have been obtained by the partial methylation of methyl α- and β-glucoheptopyranosides and methyl 2,3,4,6,7-penta-O-acetyl1-α- and-β-glucoheptopyranosides. The retention indices of both types of methyl ethers on the liquid phase NPGS have been measured and the main directions of the fragmentation of these compounds under electron impact have been determined. The laws of the mass spectra of the position isomers that have been found will permit their use in GLC-MS analysis for determining the structure of a polysaccharide by the methylation method.     

二茂镧系金属醋酸化合物的合成及稳定性

除La、Ce、Pr、Nd、Pm及Eu外,其余九种镧系金属均可生成相应的二茂镧系金属氯化物C_(p2)LnCl(Ln=Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu).二茂镧系金属氯化物不仅对水而且对空气(氧)也十分敏感,在空气中暴露很短时间,即发生分解.但它们的热稳定性均较好.由C_(p2)LnCl与NaOAc反应生成的C_(p2)ErOAc及C_(p2)YbOA_c却对空气(氧)均具有较好的稳定性,暴露在空气中48h,颜色和熔点均无明显变化.它们的热稳定性也较好,都可以在160～250℃/10~(-5)Torr下升华提纯.我们采用类似方法,合成了其余七种文献未曾报道的醋酸衍生物C_(p2)LnOAc(Ln=Sm,Gd,Tb,Dy,Ho,Tm,Lu),以考察镧系收缩对从Sm到Lu各种镧系金属二茂醋酸衍生物对空气稳定性的影响,以及它们的热稳定性.     

Studies on the melts of alkali metal acetates

The density, viscosity, and electrical conductivity of alkali metal acetates were measured over the temperature interval between melting and decomposition. The apparent activation energies of the equivalent conductivities and viscosities were calculated. It has been concluded from the results that alkali metal acetates, similarly to alkali metal benzenesulphonates studied earlier, exhibit properties quite unlike those of alkali metal halides. In the dependence of equivalent conductivity on the nature of the cation, the anomalous behaviour of lithium salts appears to be due to association prevailing in the melt phase.     

Partition high-pressure liquid-chromatographic systems for the separation of digitalis glycosides of the cardenolide group.

Several multi-component liquid-systems have been investigated on silica gel SI-60 supports of particle size 10 mum. By using two solvent systems, it was possible to separate 14 digitalis glycosides, ranging from genins of relatively low polarity to the highly polar deacetyl-lanatosides. Solvents with good ultraviolet transparency at 220 nm (lambdamax. for the butenolide ring) were chosen in order to improve the sensitivity of detection. The technique should also permit the determination of by-products and degradation products of these drug substances. Detection limits are as low as 15 ng for a 5 mul injection, and separation times vary between 4 and 20 min. The reproducibility of the retention times and the baseline separations attainable make the systems suitable for quantitative work.     

甲壳素碱介质非均相脱乙酰动力学研究

近年来,从甲壳素(聚[(1,4)-2-乙酰胺基-2-脱氧-β-D-葡萄糖])制备壳聚糖的研究和生产以及对其理论和应用的探索,越来越广泛和深入。甲壳素脱乙酰基转变成壳聚糖,由于反应条件不同,所得产品不仅结构性能不同,而且影响其深加工产品的质量.因此,对甲壳素脱乙酰基反应的研究引起国内外学者的重视.Sannan等曾报道甲壳素在碱介质中均相脱乙酰动力学的研究,但对非均相条件下脱乙酰动力学的研究,国内外至今尚未见报道.目     

Gas — Liquid chromatography — Mass spectrometry of the acetates of partially methylated methyl glycosides. II. Monomethylhexosides

Conclusions 1. Two isomers of quercetin 3-glucoside are present in the flowers and leaves of the cotton plant of variety 108-F: hirsutrin, quercetin 3--D-glucopyranoside; and isoquercitrin, quercetin 3--D-glucofuranoside.2. The quercetin 3-glucoside described by various workers under the single name isoquercitrin is a mixture of the pyranose and furanose forms, or is one of these two forms.Scientific-Research Institute for the Chemistry and Technology of Cotton Cellulose, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 555–559, September–October, 1970.     

A convenient one-pot preparation of glycosyl bromides as well as glycosyl acetates from benzyl glycosides using N-bromosuccinimide.

Some conversions of benzyl glycoside using NBS were examined and one-pot preparation of glycosyl acetates and bromides were developed. An efficient O-debenzylation at non-anomeric position was also observed.