Isomers Of Mono Research Articles

The synthesis of oligoribonucleotides. III. The use of silyl protecting groups in nucleoside and nucleotide chemistry. VIII

The synthesis of all isomeric mono- and disilyl derivatives of cytidine, guanosine, and their N-benzoyl analogues using the tert-butyldimethylsilyl protecting group is described. These compounds and those containing a 5′-monomethoxytrityl group have been condensed via the phosphodichloridite procedure to produce nucleotides rapidly and in good yields. The synthesis of 2′–5′-linked nucleotides is described. A cautionary note is introduced in regard to the preparation of 5′-monomethoxytritylguanosine and a novel methanolysis of certain N-benzoylcytidines is mentioned.

Brominated Diamino Dihydroxyanthraquinones. Blue Dyes for Synthetic‐polymer Fibres

The synthesis of all the isomeric mono‐, di‐, tri and tetrabromo derivatives of 1,8‐diamino‐4,5‐dihydroxyanthraquinone and of 1,5‐diamino‐4,8‐dihydroxyanthra‐quinones is described. The effect of the number and orientation of bromine atoms on the dyeing and fastness properties of these dyes on polyester fibres is reported. Synergistic effects pertinent to the dyeing and fastness properties of mixtures of unbrominated and brominated derivatives are also noted.

Positional isomers of unsaturated fatty acids in rat liver lipids.

The fatty acids of liver lipids from rats raised on a fat free diet from the 30th to the 90th day after birth were analyzed with special regard to the detection of positional isomers of mono-, di-, tri-, and tetraenoic fatty acids. The methyl esters obtained after transesterification of total lipids were separated by argentation chromatography into five fractions: I saturated, II monoenoic, III dienoic, IV dienoic nonmethylene interrupted, V tri- and tetraenoic fatty acid esters. After hydroxylation of the double bonds with osmium tetroxide, the analysis of the poly-O-trimethylsilyl derivatives by gas liquid chromatography on S.C.O.T. columns combined with mass spectrometry revealed the presence of 19 monoenoic, 15 dienoic, and 9 trienoic as well as 3 tetraenoic fatty acid isomers including the normally occurring representatives of the (n-3), (n-6), (n-7), and (n-9) fatty acid families. The majority of the identified isomers can be coordinated to one of these families like 7-16:1; 11-20:1; 6,9-18:2; 8,11-20:2; 5,11-20:2; 5,8,11-20:3; 7,10,13-22:3 to the (n-9) family, 11-18:1; 13-20:1; 5,11-18:2; 7,13-20:2; 6,11-18:2; 6,9-16:2; 8,11-18:2; 10,13-20:2; 5,8,11-18:3; 7,10,13-20:3; 4,7,10,13-20:4 to the (n-7) family and 11,14-20:2; 5,11,14-20:3; 6,9,12-18:3; 8,11,14-20:3; 5,8,11,14-20:4; 7,10,13,16-22:4 to the (n-6) family. All these naturally occuring isomers can be placed into a network of desaturation and chain elongation steps which allows certain conclusions about the substrate specificity of the delta6-, delta5- and delta4-desaturase systems. The great number of isomers found in the (n-7) family indicates that the members of this family are actively metabolized in partial essential fatty acid deficiency.

Application of thin-layer chromatography in the resolution of mixtures of isomeric mono- and di-aryl thioureas, thiazoles and thiazolines

Application of thin-layer chromatography in the resolution of mixtures of isomeric mono- and di-aryl thioureas, thiazoles and thiazolines

Characterization of di‐ and trimethoxybenzaldehydes by analysis of deshielding gradients obtained with Eu(fod)3 shift reagent

AbstractEu(fod)3 shift reagent was used to simplify PMR spectra from isomeric mono‐, di and trimethoxybenzaldehydes. Deshielding gradients, obtained by plotting induced shift vs. molar ratio of [Eu(fod)3]/[substrate] made it possible to assign methoxyl proton signals to the correct positional substituent in polymethoxylated benzaldehydes. Anomalous upfield shifts for the aldehydic protons of 2,6‐dimethoxy‐ and 2,4,6‐trimethoxybenzaldehyde were observed with Eu(fod)3 Various instances of long‐range (5J) proton coupling between the aldehydic proton and a meta‐proton provide insight to the geometry of the substrate in the complexed state with Eu(fod)3. Di‐ and trimethoxybenzaldehydes are important precursors for the synthesis of the correspondingly methoxylated amphetamines which are of pharmacological and forensic interest because of abuse and illicit manufacture.

Identification de dérivés nitrés aromatiques par chromatographie sur couches minces, chromatographie en phase gazeuse et par spectrométrie infrarouge

The separation of different isomers of mono- and dinitrobiphenyls has been studied by thin-layer and gas—liquid chromatography. The nitration products resulting from the action of nitric acid on biphenyl in an acetic acid solution were found to be 2,2′-, 2,4′- and 4,4′-dinitrobiphenyl. This was confirmed by comparing the infrared spectra of the isomers with those of the reference samples of the nitrobiphenyls.

Carbon‐13 chemical shifts of α,β‐unsaturated acids

AbstractCarbon‐13 spectra of 59 α,β‐unsaturated carboxylic acids have been measured. Large differential shieldings of ethylenic carbons in the cis and trans isomers of acrylic acid derivatives were found (altogether 15 isomeric Z‐ and E‐pairs of acids were investigated). The origin of differential shieldings is complex and both molecular ground states as well as changes in excited states appear to be involved. All measured 13C chemical shifts can be described by additive parameters that provide a straightforward new technique by which structural assignments can be made for a wide variety of isomeric mono‐, di‐ and tri‐ substituted α,β‐unsaturated acids.

Chromatography of isomeric peroxybenzoic acids II. The thin-layer chromatographic separation mechanism of isomeric mono- and disubstituted peroxybenzoic acids on various polyamide and cellulose adsorbents

The migration behaviour of several mono- and disubstituted peroxybenzoic acids has been studied on seven thin-layer chromatographic adsorbents. Some effects of the molecular structure of the peroxy acids on their chromatographic behaviour and the interactions between the stationary or the mobile phase and peroxy acids are discussed

Reactions of lithium-biphenyl adducts with methyl bromide and with carbon dioxide

1. Both of the phenyl rings in biphenyl participate in the formation of adducts with lithium in tetrahydrofuran. 2. In the reaction of lithium-biphenyl adducts with CH3Br with subsequent dehydrogenation a mixture of isomeric mono- and di-methylbiphenyls is formed. The hydrocarbons formed in greatest amount are 4,4'-dimethylbiphenyl, 4-methylbiphenyl, and 2,5-dimethylbiphenyl. 3. In the reaction of lithium-biphenyl adducts with CO2 we isolated two acids: 4,4'-biphenyldicarboxylic acid and an acid in which both carboxy groups are attached to the same benzene nucleus.

Alkenylation of p- and o-cresols with piperylene

1. The alkenylation of p- and o-cresols with piperylene in the presence of acid catalysts was studied. 2. Under the conditions used the reaction between p- and o-cresol and piperylene occurs as C-alkenylation. 3. The reaction products between p- and o-cresol and piperylene are isomeric mono- and diisopentenylcresols and their cyclization products-substituted chromans and coumarans.

Colourning matters of Australian plants. IV. Haemocorin: A unique glycoside from Haemodorum corymbosum Vahl

The bulbous roots of Haemodorum corymbosum Vahl. yield a red crystalline glycoside, haemocorin, which is readily hydrolysed to cellobiose and the purple-red aglycone, C20H14O4. The latter contains one methoxyl group and gives a diacetate and isomeric mono- and dimethyl ethers. The absorption spectra and other properties of these compounds suggest a polycyclic tautomeric enolone structure. Oxidation of a dimethyl ether gives a compound C22H18O7, believed to be a lactol ester, and a compound C20H14O5, which is apparently a polycyclic aromatic anhydride. These results indicate that the aglycone is a polycyclic enolic α-diketone, possibly of the indandione type.