ABSTRACT
The X-ray diffraction analysis of N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N'-p-chlorophenyloxamide (1), N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N',N'-diethyloxamide (2), N-acetyl, N-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl), N'-methyl, N'-phenyloxamide (3), N-acetyl, N-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl), N'-ethyl, N'-phenyloxamide (4) was performed. It was found that the oxamide group in compounds 1-4 can be characterized as two structurally independent amides because there is no pi conjugation across the oxalyl OC-CO bond. Only the oxamide group of 1 is planar and adopts trans conformation stabilized as two intramolecular N-H...O hydrogen bonds.
Subject(s)
Aniline Compounds/chemistry , Oxamic Acid/analogs & derivatives , Oxamic Acid/chemistry , Crystallography, X-Ray/methods , Molecular Structure , Molecular Weight , Nuclear Magnetic Resonance, Biomolecular/methodsABSTRACT
3C CP MAS NMR spectra of solid methyl 3,4,6-tri-O-acetyl-2-deoxy-2-ureido-beta-D-glucopyranosides with dipeptide residues (protected by OMe, OEt or OBz group) were recorded. Broader resonances enabled assignment of carbons linked to nitrogen. Chemical shifts of sugar carbons varied within 2-6 ppm although the acetylated glucose moiety is the same in all compounds. From the six carbonyl groups in the molecule only the resonances of N6-C5=O are shifted by 2.9-8.3 ppm downfield in the spectra of solid compounds, comparing to the solution, indicating that the molecules are linked by NH...O=C5 hydrogen bonds. The C2=O group of ureido bridge is not involved in H-bonding, ester group probably forms intramolecular H-bonds.
Subject(s)
Carbohydrates/chemistry , Dipeptides/chemistry , Glucosamine/chemistry , Magnetic Resonance Spectroscopy/methods , Urea/analogs & derivatives , Carbon Isotopes , Hydrogen Bonding , Models, Molecular , Molecular StructureABSTRACT
The X-ray diffraction analysis of methyl 2,3,6-tri-O-acetyl-2-deoxy-2-[3-(2-phenylethyl)-ureido]-beta-D- glucopyranoside has been performed, establishing that molecules are associated by two types of NH...O hydrogen bonds, N-1-H with carbonyl-oxygen and N-3-H with anomeric oxygen, with N...O distances 2.902 and 2.904 A, respectively. The urea moiety of the molecule is in anti Z,Z conformation. The signals in the 13C CP MAS NMR spectrum are neither multiplied nor split, indicating that there is one molecule in the crystal asymmetric unit. The difference in chemical shifts between solid- and liquid-state spectra are significant for C-2 and C-3 of D-glucose moiety (2.3-2.5 ppm) and for NCH2, CH2Ph carbon atoms.
