Showing papers in "Canadian Journal of Chemistry in 1982"
TL;DR: Hard-sphere exo-anomeric (HSEA) calculations have been used to predict conformers for the linear tetrasaccharide (αLRha(1.7 and 0.2 kcal/mol) as discussed by the authors, which constitutes a part of the Shigellaflexneri O-antigen.
Abstract: Hard-sphere (HS) calculations predict three conformers for the branched B human blood group antigenic determinant (α LFuc(1 → 2)[α DGal(1 → 3)]βDGal) and two conformers for the linear tetrasaccharide (αLRha(1 → 2)αLRha(1 → 3)αLRha(1 → 3)βDGlcNAc), which constitutes a part of the repeating unit of the Shigellaflexneri O-antigen, which differ in conformational energy by less than 0.7 and 0.2 kcal/mol, respectively. However, a detailed 1H nmr study of specific interunit deshielding effects, quantitative treatment of spin-lattice relaxation times, and nuclear Overhauser enhancements requires that only one of the conformers thus predicted be, in fact, conformationally preferred in solution. These conformers are those predicted by hard-sphere exo-anomeric (HSEA) calculations.
326 citations
TL;DR: In this article, the 1H and 13C nmr spectroscopy of a range of Lewis acids with crotonaldehyde was systematically investigated by 1H-and 13C-nmr spectrograms.
Abstract: 1:1 Complexes of a range of Lewis acids with crotonaldehyde (1) have been systematically investigated by 1H and 13C nmr spectroscopy. Lewis acids employed were: BF3, BCl3, BBr3, SnCl4, TiCl4, SbCl5...
239 citations
TL;DR: The South African tree Combretumcaffrum has been shown to contain a constituent capable of significantly reversing astrocyte formation employing the National Cancer Institute's 9ASK system.
Abstract: The South African tree Combretumcaffrum has been shown to contain a constituent capable of significantly reversing astrocyte formation employing the National Cancer Institute's 9ASK system. The con...
218 citations
TL;DR: The basicities of triarylphosphines P(4-XC6H4)3 (X = Cl, F, H, CH 3, CH3O, (CH3)2N), P(3-CH3C 6H4), and P(2-CH 3C7H7)3 as well as trialkylphosphine P(t-Bu)3 and PCy3 have been measured by as discussed by the authors.
Abstract: The basicities of the triarylphosphines P(4-XC6H4)3 (X = Cl, F, H, CH3, CH3O, (CH3)2N), P(3-CH3C6H4)3, and P(2-CH3C6H7)3 as well as the trialkylphosphines P(t-Bu)3 and PCy3 have been measured by th...
200 citations
TL;DR: In this paper, a procedure for the selective formation of 2′,5′-silylated ribonucleosides and 3'5'silylation was developed.
Abstract: Procedures have been developed for the selective formation of (a) 2′,5′-silylated ribonucleosides and (b) 3′,5′-silylated ribonucleosides. These procedures also permit the selective silylation at e...
195 citations
TL;DR: The use of trichloroethyl and benzyl succinimidyl carbonates for an efficient conversion of hydroxyamino acids and their esters into the corresponding N-trich chloroethoxycarbonyl and Benzyloxy Carbonyl derivatives is described.
Abstract: 9-Fluorenylmethyl succinimidyl, pentachlorophenyl, and benzotriazole-1-yl carbonates were prepared and their reactivity with L-serine and L-serine benzyl ester was compared. The most efficient reag...
181 citations
TL;DR: In this paper, three methods for estimating the pKa of a radical cation using thermochemical cycles are discussed, which enable the calculations of the pK of radical cations which have not yet been determine.
Abstract: Three methods for estimating the pKa of a radical cation using thermochemical cycles are discussed. These methods enable the calculations of the pKa of radical cations which have not been determine...
161 citations
TL;DR: In this article, 1,3-dioxolane with acetyl bromide gave (2-acetoxyethoxy)methyl bromides (2a) in 88% yield.
Abstract: Treatment of 1,3-dioxolane with acetyl bromide gave (2-acetoxyethoxy)methyl bromide (2a) in 88% yield. A number of pyrimidines and three chloropurines were trimethylsilylated and coupled with 2a. The respective N-1 and N-9 alkylated products (obtained in 79–89% yields) were deacetylated to give N-[(2-hydroxyethoxy)methyl] heterocycles. The 6-amino or 6-chloro substituent of the 2-amino-6-substituted-purine derivatives was hydrolyzed smoothly with adenosine deaminase to give 9-[(2-hydroxyethoxy)methyl]guanine (acycloguanosine), the potent antiviral agent.
142 citations
TL;DR: The FORTRAN program for refinement of stability constants from potentiometric data measured on complex systems containing any number of interacting components is described in this article, where the core algori...
Abstract: The FORTRAN program BEST for the refinement of stability constants from potentiometric data measured on complex systems containing any number of interacting components is described. The core algori...
120 citations
TL;DR: Exploded wood lignin (EXWL) was extracted from moist steam hydrolysed aspen (Populustremuloides) wood using methanol in this paper.
Abstract: Exploded wood lignin (EXWL) was extracted from moist steam hydrolysed aspen (Populustremuloides) wood using methanol. The lignin was examined by elemental analysis, gel permeation chromatography, i...
112 citations
TL;DR: The chemical synthesis of 9-[[2-hydroxy-1-(hydroxymethyl)ethoxy]methyl]guanine is described in this paper, which is a member of a class of nucleoside analogues which lack a rigid carbohydrate ring, but which possess all of the functional groups of naturally occurring deoxynucleosides.
Abstract: The chemical synthesis of 9-[[2-hydroxy-1-(hydroxymethyl)ethoxy]methyl]guanine is described. This compound, known as BIOLF-62, is active against herpesviruses. This compound is a member of a novel class of nucleoside analogues which lack a rigid carbohydrate ring, but which possess all of the functional groups of naturally occurring deoxynucleosides.
TL;DR: In this paper, solid phases in the tetrahydrofuran-water (THF-H2O) system were investigated in the temperature range 100-260 k and at pressures up to 1.5 GPa.
Abstract: Solid phases in the tetrahydrofuran–water (THF–H2O) system were investigated in the temperature range 100–260 K and at pressures up to 1.5 GPa. Thermal conductivity, λ, and heat capacity per unit v...
TL;DR: In this article, the nitrogen and β-hydrogen hyperfine splitting constants (hfsc) for various spin adducts of α-phenyl tert-butyl nitrone (PBN) and 5,5-dimethylpyrroline-Noxide (DMPO) have been obtained as a function of solvent.
Abstract: The nitrogen and β-hydrogen hyperfine splitting constants (hfsc) for phenyl, 4-nitrophenyl, 4-pyridyl, benzoyl, and trichloromethyl spin adducts of α-phenyl tert-butyl nitrone (PBN) as well as for the tert-butoxyl adduct of 5,5-dimethylpyrroline-N-oxide (DMPO) have been obtained as a function of solvent (30 solvents). A useful linear relationship between the β-H hfsc and the N-hfsc of each aminoxyl is found except for the benzoyl adduct of PBN. Some speculations regarding the structural significance of these correlations is presented.
TL;DR: In this paper, a new method for the preparation of β-chloro, β-bromo, and β-iodo α,β-unsaturated ketones is described.
Abstract: A new, efficient method for the preparation of β-chloro, β-bromo, and β-iodo α,β-unsaturated ketones is described. The method involves the reaction of β-diketones or α-hydroxymethylenecycloalkanone...
TL;DR: In this article, a new active site model for predicting and interpreting the structural and stereospecificity of horse liver alcohol dehydrogenase-catalyzed oxidations and reductions has been formulated from the specificity, X-ray, and kinetic data now available.
Abstract: A new active site model for predicting and interpreting the structural- and stereospecificity of horse liver alcohol dehydrogenase-catalyzed oxidations and reductions has been formulated from the specificity, X-ray, and kinetic data now available. The new model is based on a cubic-space system and is convenient and easy to use. The model is completely reliable and permits HLADH specificity towards all of its currently known substrates to be predicted with confidence. Its application is illustrated by analyses of representative examples of major substrate types.
TL;DR: In this article, the influence of solvent on the equilibrium position of 2,4-pentanedione was studied by calorimetric and nmr spectroscopic techniques, for solvents such as CCl4 and cyclohex.
Abstract: The influence of solvent on the equilibrium position of the tautomeric forms of 2,4-pentanedione was studied by calorimetric and nmr spectroscopic techniques. For solvents such as CCl4 and cyclohex...
TL;DR: The apparent 1-octanol/water partition coefficient (log PApp) of pentachlorophenol (PCP) varies in non-linear function with pH of the aqueous solution as discussed by the authors.
Abstract: The apparent 1-octanol/water partition coefficient (log PApp) of pentachlorophenol (PCP) varies in non-linear function with pH of the aqueous solution. In the range of pH 1.2 to 13.5 extreme values...
TL;DR: A new algorithm for the simultaneous determination of any number of protonation constants from potentiometric equilibrium data is described, characterized by a unique approach to the internal refinement of the constants and by the analytical nature of the numerical analysis whereby minimization is sought and achieved on the residuals between calculated and observed pH.
Abstract: A new algorithm for the simultaneous determination of any number of protonation constants from potentiometric equilibrium data is described. This algorithm is characterized by a unique approach to ...
TL;DR: In this paper, the thermal degradation of EDTA chelates was investigated in alkaline aqueous solution at elevated temperatures (230-310 °C) and the kinetics of decomposi...
Abstract: The thermal degradation of Ca(II), Mg(II), Zn(II), Fe(II), and Ni(II) chelates of EDTA was investigated in alkaline aqueous solution at elevated temperatures (230–310 °C). The kinetics of decomposi...
TL;DR: Treatment of Ru3(CO)8(μ3-η2-C≡CR)(μ2-PPh2)(R = But, Pri) with dihydrogen liberates olefin (CH2=CHR) and generates the coordinatively unsaturated cluster Ru3[CO]9(μ2]-PPh 2)(μ 2-H) which has been shown as mentioned in this paper.
Abstract: Treatment of Ru3(CO)8(μ3-η2-C≡CR)(μ2-PPh2)(R = But, Pri) with dihydrogen liberates olefin (CH2=CHR) and generates the coordinatively unsaturated cluster Ru3(CO)9(μ2-PPh2)(μ2-H) which has been shown
TL;DR: Protection of the nucleosides as p-toluyl esters provided reactants that were soluble in organic solvents and crystallized readily in high yields.
Abstract: Treatment of uracil bases and protected nucleosides with iodine monochloride (ICl) gave the corresponding 5-iodouracil products in over 95% purified yields. Analogously facile chlorination was effe...
TL;DR: The present procedure, which eliminates most of the uncertainties in the original Hopp–Woods method, leads to a very satisfactory prediction of the antigenic determinants.
Abstract: The locations of the antigenic determinants in a protein are predicted from its amino acid sequence by a modified Hopp–Woods method, proposed in this work, using both hydrophihcity and recognition factors. The amino acid – amino acid interaction energies, from which the recognition factors have been defined, have been evaluated by a semiempirical method, developed at this laboratory, using 1/R expansions parameterized on the basis of the results from accurate SCF calculations. The present procedure, which eliminates most of the uncertainties in the original Hopp–Woods method, leads to a very satisfactory prediction of the antigenic determinants.
TL;DR: A computer program written in BASIC is presented for the simulation of isotropic spectra using a microprocessor, where the capabilities of much larger FORTRAN programs, run on mainframe computers, are retained in the more restricted environment of the microprocessor.
Abstract: A computer program written in BASIC is presented for the simulation of isotropic esr spectra using a microprocessor. Since BASIC is the most common microprocessor language, this program can easily ...
TL;DR: In this paper, a flow calorimeter and a flow densimeter were used to measure the heat capacities and densities of aqueous solutions of H3PO4, NaH2PO4 and Na2HPO4.
Abstract: Measurements at 25 °C with a flow calorimeter and a flow densimeter have led to heat capacities and densities of aqueous solutions of H3PO4, NaH2PO4, Na2HPO4, Na3PO, NaHCO3, Na2CO3, H2SO4, and vari...
TL;DR: In this paper, the effects on ionic heats of formation of the multiple substitution of -CH3, -OH, or -OCH3 groups, in place of H atoms, are described.
Abstract: The effects on ionic heats of formation of the multiple substitution of -CH3, -OH, or -OCH3 groups, in place of H atoms, are described. It is shown that for all three substituents, good linear corr...
TL;DR: The infrared spectral properties of N-(2-hydroxybenzylidene)-m-toluidine, and their photoproducts have been investigated in this paper.
Abstract: The infrared spectral characteristics of N-(2-hydroxybenzylidene)aniline, its deuterium substituted analogue, N-(2-hydroxybenzylidene)-m-toluidine, and their photoproducts have been investigated. The infrared spectrum of a low temperature polycrystalline film of N-(2-hydroxybenzylidene)aniline exhibits new absorption bands at 3380, 1646, 1537, 1502, 1319, and 1310 cm−1 upon irradiation at 365 nm. Likewise, the spectrum of the m-toluidine derivative exhibits new absorption bands at 3320, 1650, 1535, 1503, 1321, 1310, and 995 cm−1 upon irradiation at 365 nm. These new data, in conjunction with the newly acquired data on the hydrochloride and deuterochloride of the title compound, indicate that the photoproduct is a zwitterion, not an ortho-quinone. It is also inferrred that the photoproduct exists in a conformation which is cis about the central carbon–nitrogen double bond.
TL;DR: Several syntheses of the previously unknown 1,2dihydro-3H-pyrrolo[1,2a]pyrrole-1-carboxylic acid and various 5- and 6-substituted derivatives thereof have been devised as mentioned in this paper.
Abstract: Several syntheses of the previously unknown 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acid and various 5- and 6-substituted derivatives thereof have been devised. Some of these processes ha...
TL;DR: In this article, a flow microcalorimeter and vibrating tube densimeter were used to obtain apparent molal heat capacities and volumes of aqueous NaHS and Na2S from 0.1 to 1.0
Abstract: A flow microcalorimeter and vibrating tube densimeter were used to obtain apparent molal heat capacities and volumes of aqueous NaHS and Na2S from 0.1 to 1.0 mol kg−1 and of aqueous H2S from 0.03 t...
TL;DR: In this article, the equilibrium constants K 1 for reaction [1] RH+Cl−Cl−−=RHCl− in the gas phase were measured with a high pressure mass spectrometer under chemical ionization conditions.
Abstract: Equilibrium constants K1 for reaction [1] RH + Cl− = RHCl− in the gas phase were measured with a high pressure mass spectrometer under chemical ionization conditions. Data for some 40 compounds RH ...
TL;DR: In this paper, two reaction routes for the preparation of hexa-O-acetyl-2deoxy-2-phthalimido-β-D-lactosyl chloride from lactal hexaacetate were presented.
Abstract: Two reaction routes are presented for the preparation of hexa-O-acetyl-2-deoxy-2-phthalimido-β-D-lactosyl chloride (7) from lactal hexaacetate (1). One route involves, in the first stage, reaction ...