197575-49-8

Upstream product

• 263273-82-1 [1,2-¹⁷O₂]benzoic acid 

Downstream Products

• 1237512-20-7 C₁₄H₁₉NO⁽¹⁷⁾O 

Relevant academic research and scientific papers

Solid-State 17O NMR Investigation of the Carbonyl Oxygen Electric-Field-Gradient Tensor and Chemical Shielding Tensor in Amides

We have presented a systematic experimental and theoretical investigation of the carbonyl oxygen electric-field-gradient (EFG) tensor and chemical shielding (CS) tensor in crystalline amides. Three 17O-labeled secondary amides, R1C[17O]-NHR2, have-been synthesized: benzanilide (1), N-methylbenzamide (2), and acetanilide (3). Analysis of 17O magic-angle spinning (MAS) and stationary NMR spectra yields not only the magnitude but also the orientation of the carbonyl 17O EFG and CS tensors. For compounds 1-3, the carbonyl 17O quadrupolar coupling constant (QCC) and the span of the chemical shift tensor are found to be in the range of 8.5-8.97 MHz and 560-630, ppm, respectively. The largest 17O EFG component lies in the amide plane and is perpendicular to the C=O bond, whereas the smallest component is perpendicular to the N-C=O plane. For the carbonyl 17O CS tensor, the principal component with the largest shielding, δ33, is perpendicular to the amide plane, and the tensor component corresponding to the least shielding, δ11, is in the amide plane approximately 20 off the direction of the C=O bond. Extensive quantum chemical calculations using density functional theory (DFT) have been performed for both isolated and hydrogen-bonded molecules of compounds 1-3. The calculated carbonyl 17O EFG and CS tensors from the latter molecular models are in reasonably good agreement with the experimental values. In particular, the B3LYP/D95** EFG calculations overestimate the carbonyl 17O QCC by approximately 0.5 MHz. The B3LYP/D95**/GIAO shielding calculations yield a linear correlation between the calculated and experimental data (slope=1.125 and R2=0.9952). The quantum chemical calculations indicated that the intermolecular C=O...H-N hydrogen-bonding interactions play an important role in determining the carbonyl oxygen EFG and CS tensors for an amide functional group.

Orientations of the 17O electric-field-gradient tensor and chemical shift tensor in benzamide: NMR of dipolar coupled spins

We report a solid-state 17O NMR study of [α-13C,17O] benzamide. The orientations of the 17O electric-field-gradient and chemical shift tensors were determined from analysis of magic-angle spinning and stationary 17O NMR spectra. The largest electric-field-gradient component lies in the amide plane and perpendicular to the 13C-17O dipolar vector, whereas the intermediate electric-field-gradient component is along the C=O bond. It is also found that the principal component of the 17O chemical shift tensor with the least shielding, δ11, is approximately 18° off the C=O bond and that the component with the most shielding, δ33, is perpendicular to the amide plane. The present study confirms our earlier results of quantum chemical calculations.

Stereodefined synthesis of O3′-labeled uracil nucleosides. 3′-[17O]-2′-azido-2′-deoxyuridine 5′-diphosphate as a probe for the mechanism of inactivation of ribonucleotide reductases

Thermolysis of a 2′-[16O]-O-benzoyl-[17O]-5′-O-(tert- butyldimethylsilyl)-O2,3′-cyclouridine derivative gave the more stable 3′-[17O]-O-benzoyl-[16O]-5′-O-(tert- butyldimethylsilyl)-O2,2′-cyclouridine isomer, which was converted into 3′-[17O]-2′-azido-2′-deoxyuridine by deprotection and nucleophilic ring opening at C2′ with lithium azide. The 5′-diphosphate was prepared by nucleophilic displacement of the 5′-O-tosyl group with tris(tetrabutylammonium) hydrogen pyrophosphate. Model reactions gave 16O and 18O isotopomers, and base-promoted hydrolysis of an O2,2′-cyclonucleoside gave stereodefined access to 3′-[18O]-1-(β-D-arabinofuranosyl)uracil. Inactivation of ribonucleoside diphosphate reductase with 2′-azido-2′-deoxynucleotides results in appearance of EPR signals for a nitrogen-centered radical derived from azide, and 3′-[17O]-2′-azido-2′-deoxyuridine 5′-diphosphate provides an isotopomer to perturb EPR spectra in a predictable manner.