scholarly journals RING CONTRACTION DURING THE LEAD TETRAACETATE OXIDATION OF REDUCING SUGARS

1964 ◽  
Vol 42 (11) ◽  
pp. 2365-2374 ◽  
Author(s):  
A. S. Perlin
Keyword(s):  
Reducing Sugars ◽  
Acyl Migration ◽  
Large Change ◽  
High Reactivity ◽  
Membered Ring ◽  
Lead Tetraacetate ◽  
The Other ◽  
Concentration Change ◽  
Pyranose Form ◽  
Cleavage Step

The rate of oxidation of D-glucose by lead tetraacetate in acetic acid is affected little by a large change in concentration of reactants, showing that the glycol cleavage step is not rate-controlling. Oxidation of 3-O-methyl-6-O-trityl-D-glucose yields 3-O-formyl-2-O-methyl-5-O-trityl-D-arabinose; the latter is not derived by production initially of a 4-O-formyl derivative that undergoes acyl migration. It is probable that the oxidation of D-glucose proceeds with conversion of the pyranose sugar into a furanose intermediate. By contrast, D-mannose appears to be oxidized mainly in the pyranose form, as shown by the oxidation patterns of D-mannose-1- and -2-14C and 5-O-methyl-D-mannofuranose, and the effects of concentration change on the reaction of D-mannose and derivatives. The proximity of the ring oxygen atom to the 1,2-diol group may contribute to the unusually high reactivity of D-mannopyranose as compared with other types of monocyclic six-membered ring vic-diols.Intermediate proportions of furanose and pyranose pathways characterize the lead tetraacetate oxidation of the other six aldohexoses. Similarities in the behavior of glucose and idose, gulose and mannose, and allose and talose may originate in steric similarities between these pairs of sugars.

REACTIONS OF OXODELCOSINE AND INTERRELATION OF DELCOSINE AND DELSOLINE

1960 ◽  
Vol 38 (12) ◽  
pp. 2433-2440 ◽  
Author(s):  
Vinko Skarić ◽  
Léo Marion
Keyword(s):  
Sodium Borohydride ◽  
Membered Ring ◽  
Lead Tetraacetate ◽  
The Other ◽  
Supporting Evidence ◽  
Close Relationship ◽  
Suggested Structure ◽  
Hydrolysis Of

The oxidation of diacetyldelcosine produces a lactam which, after hydrolysis of the acetyl groups, can be oxidized further to a diketo-lactam in which one of the keto groups is in a five- and the other in a six-membered ring. This result leads to an alteration of the previously suggested structure of delcosine. The new structure suggests a close relationship between delcosine and delsoline which is confirmed by the methylation of the former. The reaction is selective and gives rise to a monomethyldelcosine identical in every way with delsoline. Reduction of the diketo-lactam (didehydro-oxodelcosine) with sodium borohydride gives oxodelcosine. Dehydro-oxodelcosine is also described, and its oxidation with lead tetraacetate as well as that of oxodelcosine lead to the formation of keto-products which lend supporting evidence for the structure assigned to delcosine.

REACTION OF ALDOSES AND KETOSES WITH LEAD TETRAACETATE

1956 ◽  
Vol 34 (4) ◽  
pp. 541-553 ◽  
Author(s):  
A. S. Perlin ◽  
Carol Brice
Keyword(s):  
Lower Order ◽  
Higher Order ◽  
Lead Tetraacetate ◽  
Pyranose Form ◽  
Reaction Proceeds ◽  
Furanose Form ◽  
Rare Sugars

Lead tetraacetate is highly selective for oxidation of α-hydroxy-hemiacetal groups and hence most readily attacks cyclic forms of the sugars. The reaction proceeds stepwise; the hemiacetal α-glycol being cleaved and the monoester of a correspondingly shorter-chained sugar formed. After cyclization the new sugar in turn is oxidized at the hemiacetal α-glycol group to yield a diester of a still-lower-order member of the series. In this manner D-glucose first yields mono-O-formyl-D-arabinose and then di-O-formyl-D-erythrose. Similarly, D-fructose is degraded to a glycolate ester of D-erythrose and finally to a formate–glycolate diester of D-glyceraldehyde. Some relatively rare sugars thus may conveniently be prepared directly from abundant higher-order members of the series. The reactions appear to involve preferential attack of the furanose form of a sugar rather than of the normally-predominant pyranose form, or possibly migration of ester groups towards the reducing end of the sugars.

scholarly journals Di-μ-chlorido-bis{[2-(di-tert-butylphosphanyl)biphenyl-3-yl-κ2C3,P]palladium(II)} dichloromethane disolvate

2013 ◽  
Vol 69 (2) ◽  
pp. m86-m86 ◽  
Author(s):  
Cedric W. Holzapfel ◽  
Bernard Omondi
Keyword(s):  
Palladium Complex ◽  
Solvent Molecule ◽  
Membered Ring ◽  
The Other ◽  
Coordination Geometry ◽  
Inversion Center ◽  
Asymmetric Unit ◽  
Coordination Sites ◽  
Square Planar ◽  
Cl Atoms

The asymmetric unit of the title compound, [Pd2Cl2(C20H26P)2]·2CH2Cl2, contains one half-molecule of the palladium complex and a dichloromethane solvent molecule. In the complex, two PdIIatoms are bridged by two Cl atoms, with the other two coordination sites occupied by a C atom of the biphenyl system and a P atom, resulting in a distorted square-planar coordination geometry of the PdIIatom and a cyclometallated four-membered ring. The Pd2Cl2unit is located about an inversion center. The planes of the rings of the biphenyl system make a dihedral angle of 66.36 (11)°.

Total Diet Study: Carbohydrate Content and Methodology

1964 ◽  
Vol 47 (5) ◽  
pp. 823-826
Author(s):  
James F Eheart ◽  
Blanche S Mason
Keyword(s):  
Reducing Sugars ◽  
Starch Content ◽  
The Other ◽  
Total Sugars ◽  
Total Diet Study ◽  
Factor Effect ◽  
Total Diet ◽  
Extreme Variability ◽  
Diet Study ◽  
Positive Correlations

Abstract Determinations were made of total and reducing sugars, sucrose, dextrin, and starch content of dry fat-free solids of the "total diet" samples previously reported by Food and Drug Administration. Samples represented differences in season, location, time of purchase, and store at which purchased. Mean dry fat-free solids contents did not differ significantly. Purchase periods and locations caused extreme variability of the sucrose content of the diets. Factor- effect variations among the other carbohydrate constituents were not considered nutritionally important. Reducing sugars, sucrose, and starch gave positive correlations with total sugars, while negative correlations were obtained for total sugars with dextrin and for reducing sugars with sucrose.

Mesitylene Osmium(II) Complexes Containing the Functional Phosphane tBuP(CH2CO2Me)2 and Anionic Species Derived Thereof as Bi- and Tridentate Ligands

1998 ◽  
Vol 53 (5-6) ◽  
pp. 540-544 ◽  
Author(s):  
Gerhard Henig ◽  
Helmut Werner
Keyword(s):  
Membered Ring ◽  
Chelate Complex ◽  
The Other ◽  
Quantitative Yield ◽  
Partial Hydrolysis ◽  
Neutral Complex ◽  
Ligand Complex ◽  
Tridentate Ligands ◽  
Tripodal Ligand ◽  
Anionic Species

Abstract The dichloroosmium(II) compound [(mes)OsCl2(L)] (2) with L = tBuP(CH2CO2Me)2 reacts with one or two equivalents of AgPF6 to give the mono- or dicationic complexes 3 and 4 containing the phosphanediyldiester as a bi- or tridentate chelating ligand. Complex 4 undergoes, in the presence of water, partial hydrolysis to give the difluorophosphatoosmium(II) derivative 5 in quantitative yield. Treatment of 4 with two equivalents of KOtBu affords by deprotonation at both CH2 groups of L the neutral complex 6, in which one PCHCO2Me unit of the dianionic ligand |tBuP(CHCO2Me)2]2- forms a five-membered and the other PCHCO2Me unit a three-membered ring with the metal. The reaction of 6 with water leads selectively to the formation of the chelate complex 7 containing the phosphanediylbis(carboxylate) [tBuP(CH2CO2)2]2- as a tripodal ligand.

The synthesis, separation, and identification of the methyl ethers of arabinose and their derivatives

1967 ◽  
Vol 45 (3) ◽  
pp. 275-290 ◽  
Author(s):  
S. C. Williams ◽  
J. K. N. Jones
Keyword(s):  
Reducing Sugars ◽  
Reducing Sugar ◽  
The Other ◽  
Partition Chromatography ◽  
Ring Form ◽  
Optical Rotations ◽  
Layer Chromatography ◽  
Derivatives Of ◽  
Spray Reagents

A study has been made of various methods available for the identification and separation of the methyl ethers of arabinose. Gas–liquid partition chromatography has been used to separate the acetylated glycosides and the acetylated alditols of the methyl ethers of arabinose. All of the methyl ethers of arabinopyranose and arabinofuranose have been separated by paper chromatography. Several spray reagents have been used to distinguish between those methyl ethers with similar rates of movement. Thin-layer chromatography has been used to separate the methyl glycosides, acetylated methyl glycosides, and glycitols of the methyl ethers of arabinose, as well as the methyl ethers of the reducing sugar. The optical rotations of the reducing sugars and of the methyl glycosides of the methyl ethers of arabinose provide information about the ring form and, in the case of the glycosides, about the anomer present. The rotations of the acetylated and unacetylated O-methyl arabinitols aid in the determination of the position of the methyl substitutents. In connection with this study, all of the mono-O-methyl and tri-O-methyl, and most of the di-O-methyl ethers of arabinose have been synthesized. New syntheses have been devised for 4-O-methyl and 2,3-di-O-methyl arabinose, and the other sugars have been synthesized by known or partially revised syntheses. During this work, previously unreported derivatives of these sugars have been prepared.

scholarly journals (1R,4R,6S,7R)-5,5-Dibromo-1,4,8,8-tetramethyltricyclo[5.4.1.04,6]dodecan-12-one

2014 ◽  
Vol 70 (5) ◽  
pp. o526-o526 ◽  
Author(s):  
Mohamed Zaki ◽  
Ahmed Benharref ◽  
Jean-Claude Daran ◽  
Moha Berraho
Keyword(s):  
Title Compound ◽  
Chair Conformation ◽  
Membered Ring ◽  
The Other ◽  
Boat Conformation ◽  
Asymmetric Unit ◽  
Cedrus Atlantica ◽  
Compound C ◽  
Independent Molecules

The title compound, C16H24Br2O, was synthesized from the reaction of β-himachalene (3,5,5,9-tetramethyl-2,4a,5,6,7,8-hexahydro-1H-benzocycloheptene), which was isolated from Atlas cedar (Cedrus atlantica). The asymmetric unit contains two independent molecules with similar conformations. Each molecule is built up from two fused seven-membered rings and an additional three-membered ring. In both molecules, one of the seven-membered rings has a chair conformation, whereas the other displays a screw-boat conformation.

THE NUTRITION OF PHYTOPHTHORA

1956 ◽  
Vol 34 (5) ◽  
pp. 751-757 ◽  
Author(s):  
L. E. Lopatecki ◽  
William Newton
Keyword(s):  
Ammonium Salt ◽  
Organic Nitrogen ◽  
Reducing Sugars ◽  
The Other ◽  
Phytophthora Cactorum ◽  
Sugar Consumption ◽  
Sugar Utilization ◽  
Thiamine Content ◽  
Thiamine Level ◽  
Bio Assay

Phytophthora cactorum grew well in ammonium–salt media but not in nitrate. Conversely, P. megasperma grew well in nitrate but not in ammonium–salt media. P–parasitica and P. erythroseptica grew well in both, but better in that containing nitrate. All species grew better in the presence of organic nitrogen. Evidence is presented that iron, zinc, copper, and manganese are essential trace metals and that zinc is required in greater concentrations than iron. The optimum requirement for glucose or sucrose was found to be approximately 4%, and the residual sucrose was converted into reducing sugars by all species except P. cactorum. Approximately 50% of the residual sugar remained unchanged in the cultures of this species. The growth rate and sugar consumption increased as the thiamine level was increased from 0.2 to 0.8 mgm. per liter, but the coefficient of sugar utilization remained constant. On the other hand, the percentage of nitrogen in the mycelium decreased markedly as the thiamine content of the medium was increased. It is concluded that with media containing 1% alanine an accurate bio-assay of thiamine can be made over a concentration range of 0,2 to 0.6 mgm. per liter.

scholarly journals Crystal structure and solvent-dependent behaviours of 3-amino-1,6-diethyl-2,5,7-trimethyl-4,4-diphenyl-3a,4a-diaza-4-bora-s-indacene

2017 ◽  
Vol 73 (3) ◽  
pp. 378-382
Author(s):  
Lijing Yang ◽  
Brett Drew ◽  
Ravi Shekar Yalagala ◽  
Rameez Chaviwala ◽  
Razvan Simionescu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fluorescence Spectroscopy ◽  
Title Compound ◽  
Nmr Spectra ◽  
Membered Ring ◽  
The Other ◽  
Time Dependent ◽  
H Nmr ◽  
The Mean ◽  
Over Time

In the title compound (3-amino-4,4-diphenyl-BODIPY), C28H32BN3, the central six-membered ring has a flattened sofa conformation, with one of the N atoms deviating by 0.142 (4) Å from the mean plane of the other five atoms, which have an r.m.s. deviation of 0.015 Å. The dihedral angle between the two essentially planar outer five-membered rings is 8.0 (2)°. In the crystal, molecules are linkedviaweak N—H...π interactions, forming chains along [010]. The compound displays solvent-dependent behaviours in both NMR and fluorescence spectroscopy. In the1H NMR spectra, the aliphatic resonance signals virtually coalesce in solvents such as chloroform, dichloromethane and dibromoethane; however, they are fully resolved in solvents such as dimethyl sulfoxide (DMSO), methanol and toluene. The excitation and fluorescence intensities in chloroform decreased significantly over time, while in DMSO the decrease is not so profound. In toluene, the excitation and fluorescent intensities are not time-dependent. This behaviour is presumably attributed to the assembly of 3-amino-4,4-diphenyl-BODIPY in solution that leads to the formation of noncovalent structures, while in polar or aromatic solvents, the formation of these assemblies is disrupted, leading to resolution of signals in the NMR spectra.

Note: The effect of Ethephon on the colour, composition and quality of mango (Mangifera indica, cv Kent) / Nota: Efecto del Ethephon sobre el color, la composición y la calidad del mango (Mangifera indica cv Kent)

1998 ◽  
Vol 4 (3) ◽  
pp. 199-205 ◽  
Author(s):  
A.R. Centurión Yah ◽  
S.A. González Novelo ◽  
J.A. Tamayo Cortés ◽  
J.J. Argumedo ◽  
E. Sauri Duch
Keyword(s):  
Chemical Composition ◽  
Vitamin C ◽  
Reducing Sugars ◽  
Mangifera Indica ◽  
The Other ◽  
Soluble Solids ◽  
Ripe Fruit ◽  
Yellow Colour ◽  
General Acceptance

Mango cv Kent, as grown on the Yucatan Peninsula, despite its satisfactory ripening, pleasant flavour, correct pulp colour and general acceptance, shows a skin without the characteristic red- yellow colour of the regular ripe fruit; it remains green and this makes it slightly unattractive to the consumer. On the other hand, ethylene and some other components such as Ethephon, have been used to homogenize the ripening in many fruits and to improve its colour. This work shows the results of the effect of nine different treatments with Ethephon on the colour, composition and quality of mango cv Kent. Fruit was treated by immersion in solutions of Ethephon at three different concentrations (500, 1500 and 2000 ppm) and for three different lengths of times (3, 6 and 9 min). The colour improvement depended upon the concentration and time of the treatment with Ethephon. In general, it was found that treatment with Ethephon had a significantly posi tive effect on the colour of the mango skin, as it caused the degradation of chlorophyll, which gave the appearance of the characteristic yellow and red colours to 100% of the fruit treated with 2500 ppm. Treatments influenced significantly the chemical composition of the pulp, particularly the concentration of total soluble solids, reducing sugars, carotenoids, vitamin C and acidity. The best sensorial acceptance was obtained from treatments with 1500 ppm.

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