K.G.R. Pachler

P.M.R. spectroscopy of monomethyl ethers of D-galactopyranose and its derivatives

Abstract P.m.r. parameters determined at 100 MHz for solutions in deuterium oxide) are presented for trimethyl ethers of D -galactopyranoside (eight), methyl D -galactopyranoside (eight), and galactitol (four). The anomeric and methoxyl proton chemical-shifts of these compounds are compared with those of the corresponding mono-, di-, and tetra-methyl ethers of D -galactopyranose and its derivatives. The results in this and earlier papers show that anomeric change greatly affects the 2-methoxyl signals (in derivatives of D -galactose, D -glucose, and D -mannose); change in configuration at C-4 ( D -galactose compared with D -glucose) affects the neighboring 3-methoxyl signal much more than the 4-methoxyl signal.

Characterisation of methyl derivatives of d-galactopyranose and methyl ethers of galactitol by p.m.r. spectroscopy

Abstract The 60- and 100-MHz p.m.r. spectra of methyl 2,3,4,6-tetra-O-methyl-α- d -galactopyranoside (1) and methyl 2,3,4,6-tetra-O-methyl-β- d -galactopyranoside (2) (dissolved in benzene, deuterium oxide, and other solvents) have been analysed for their methoxyl and anomeric proton signals, and compared with the spectra of the corresponding d -glucose derivatives, namely, methyl 2,3,4,6-tetra-O-methyl-α- d -glucopyranoside (3) and methyl 2,3,4,6-tetra-O-methyl-β- d -glucopyranoside (4). The spectrum of a mixture of 2,3,4,6-tetra-O-methyl-α- d -galactopyranose (5) and 2,3,4,6-tetra-O-methyl-β- d -galactopyranose (6) was obtained similarly, and the signals for all eight methoxyl groups were assigned for solutions in benzene and deuterium oxide. The spectra of 2,3,4,6-tetra-O-methyl- d -galactitol (7) and hexa-O-methylgalactitol (8) were analysed for their methoxyl-group signals in six solvents; these were assigned by using derivatives of 7 and 8 in which CH3O groups were replaced by CD3O groups to different extents. Compared with the use of the spectra of 1 and 2, the use of the p.m.r. spectrum of 7 (dissolved in benzene) was found to be a relatively simple method for identification of an unknown methyl ether of d -galactopyranose. The dependence of the spectra of the d -galactose derivatives (1, 2, 5, 6, 7 and 8) on concentration was measured for benzene solutions at 60 MHz; the spectra of these compounds in the other solvents used showed negligible dependence on concentration.

P.m.r. Spectroscopy of trimethyl ethers of D-galactopyranose its derivatives

Abstract P.m.r. parameters determined at 100 MHz for solutions in deuterium oxide) are presented for trimethyl ethers of D -galactopyranoside (eight), methyl D -galactopyranoside (eight), and galactitol (four). The anomeric and methoxyl proton chemical-shifts of these compounds are compared with those of the corresponding mono-, di-, and tetra-methyl ethers of D -galactopyranose and its derivatives. The results in this and earlier papers show that anomeric change greatly affects the 2-methoxyl signals (in derivatives of D -galactose, D -glucose, and D -mannose); change in configuration at C-4 ( D -galactose compared with D -glucose) affects the neighboring 3-methoxyl signal much more than the 4-methoxyl signal.

Conformational analysis of 1,2:3,4-di-O-isopropylidene-α-d-galacto-octopyranose derivatives: a 1H- and 13C-N.M.R.-spectral and x-ray comparative study

Abstract The pyranoid conformations of 7-acetamido-6,7,8-trideoxy-1,2:3,4-di- O -isopropylidene- d - glycero -α- d - galacto -octopyranose ( 3 ) and 7-acetamido-7,8-dideoxy-1,2:3,4-di- O -isopropylidene- l - threo -α- d - galacto -octopyranose ( 4 ) in solution have been determined by calculation of the dihedral angles from the vicinal, proton-proton coupling-constants, using three modifications of the Karplus equation. Of these, only the equation 3 J (HCCH)(φ)  (7.48  0.74 -ΣδE x )  (2.03  0.17 ΣE x )cos φ + (4.60  0.23 ΣδE x )cos 2φ + 0.06 (Σ ± ΔE x )sin φ + 0.62 (Σ ± ΔE x )sin 2φ indicates that the pyranoid part of 3 and 4 has the ° S 2 conformation, very slightly distorted towards ° H 5 , in agreement with the conformations determined for the crystalline state. Analysis of the 1 H-n.m.r. data for a series of 1,2:3,4-di- O -isopropyl-idene-α- d - galacto -octopyranose derivatives shows that the pyranoid parts of these compounds adopt the same conformation as that found for 3 and 4 .

P.M.R. spectroscopy of O-methyl derivatives of d-galactopyranose and related compounds in solution in deuterium oxide

Abstract The results obtained from a study of the p.m.r. spectroscopy of deuterium oxide solutions of d -galactopyranose and its partially and fully methylated derivatives are discussed. The methoxyl-proton chemical-shifts for some of these compounds are compared with those of corresponding derivatives of d -glucose, d -mannose, and the hydrochlorides of 2-deoxy-2-(methylamino)- d -glucose and - d -galactose. The effects, on the methoxyl and anomeric proton chemical-shifts, of anomeric change, methylation of neighboring hydroxyl groups, and change in configuration of adjacent carbon atoms bearing a hydroxyl or methoxyl group are noted.

INDO MO calculations of the electronic structures of pyrolle, imidazole, and derivatives

Abstract INDO MO calculations on a series of N-substituted pyrroles and imidazoles have been analysed for substituent effects. Some of the basic characteristics of the σI and σR0 parameters are reflected in the calculated electron densities of the compounds studied. For example, good correlations are obtained between Δqσ N(1)/ΣΔqσ parameters and σI for the R substituted compounds, as well as between ΣΔqπ values and σR0 for the + R derivatives. The + R substituents lead to an increased localization of the π-bonds, whereas R substituted derivatives show an increased delocalization, i.e., the π-bond orders across C(2)C(3) [or C(2)N(3)] and C(4)C(5) decrease and those across other bonds in the ring increase.