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PURPOSE:To test the feasibility of semi-quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters for evaluating tumor hypoxia in a maxillofacial VX2 rabbit model. METHODS:Eight New Zealand rabbits were inoculated with VX2 cell solution to establish a maxillofacial VX2 rabbit model. DCE-MRI were carried out using a 1.5 Tesla scanner. Semi-quantitative DCE-MRI parameters, maximal enhancement ratio (MER) and slope of enhancement (SLE), were calculated and analyzed. The tumor samples from rabbits underwent hematoxylin-eosin (HE), pimonidazole (PIMO) and vascular endothelial growth factor (VEGF) immunohistochemistry (IHC) staining, and the PIMO area fraction and VEGF IHC score were calculated. Spearman's rank correlation analysis was used for statistical analysis. RESULTS:The MER values of eight VX2 tumors ranged from 1.132 to 1.773 (1.406 ± 0.258) and these values were negatively correlated with the corresponding PIMO area fraction (p = 0.0000002), but there was no significant correlation with the matched VEGF IHC score (p = 0.578). The SLE values of the eight VX2 tumors ranged from 0.0198 to 0.0532 s(-1) (0.030 ± 0.011 s(-1)). Correlation analysis showed that there was a positive correlation between SLE and the corresponding VEGF IHC score (p = 0.0149). However, no correlation was found between SLE and the matched PIMO area fraction (p = 0.662). The VEGF positive staining distribution predominantly overlapped with the PIMO adducts area, except for the area adjacent to the tumor blood vessel. CONCLUSIONS:The semi-quantitative parameters of DCE-MRI, MER and SLE allowed for reliable measurements of the tumor hypoxia, and could be used to noninvasively evaluate hypoxia during tumor treatment.

PurposeThis study aimed to compare dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with T2-weighted imaging (T2WI) for the preoperative staging of early endometrial carcinoma.MethodsThis retrospective study included 22 subjects with early endometrial carcinoma who underwent 3.0 T MRI examination prior to hysterectomy. DCE-MRI and T2WI were evaluated for the preoperative staging of endometrial carcinoma. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of DCE-MRI and T2WI were assessed and compared using the revised International Federation of Gynecology and Obstetrics surgical staging guidelines (2009) as the reference standard.ResultsOut of the 22 cases of endometrial carcinoma, the use of the reference standard method led to the staging of 14 as IA and eight as IB. The sensitivity, specificity, PPV, NPV, and accuracy of DCE-MRI for preoperative staging were 100% (95% confidence interval: 0.73-1.0), 62.5% (95% CI: 0.26-0.90), 82.4% (95% CI: 0.56-0.95), 100% (95% CI: 0.46-1.0), and 86.4%, respectively, and these values were 85.7% (95% CI: 0.56-0.97), 75% (95% CI: 0.36-0.96), 85.7% (95% CI: 0.56-0.97), 75% (95% CI: 0.36-0.96), and 81.8%, respectively, for T2WI. Thus, the sensitivity and accuracy of DCE-MRI were greater than those of T2WI for preoperative endometrial carcinoma staging.ConclusionDCE-MRI was more sensitive but less specific than T2WI for the preoperative staging of early endometrial carcinoma. DCE-MRI may serve as a useful and reliable tool for the preoperative assessment of endometrial carcinoma.

Enantiopure monohydrosilanes are versatile chiral reagents for alcohol resolution and mechanistic investigation. Herein, we have demonstrated the asymmetric synthesis of monohydrosilanes via an intramolecular hydrosilylation strategy. This protocol is suitable for the synthesis of five‐ and six‐membered cyclic monohydrosilanes, including a class of chiral oxasilacycles, with excellent diastereo‐, regio‐, and enantioselectivities. Notably, the catalyst loading could be reduced to 0.1 mol % which makes this one of the most efficient methods to access chiral monohydrosilanes. Mechanistic studies and DFT calculations indicate this Rh‐catalyzed intramolecular asymmetric hydrosilylation reaction might proceed via a Chalk–Harrod mechanism, and the enantio‐determining step was predicted to be oxidative addition of Si−H bond. [ABSTRACT FROM AUTHOR]

A highly enantioselective tandem Pudovik addition/[1,2]-phospha-Brook rearrangement of α-alkynylketoamides with diarylphosphine oxides was achieved with a N,N'-dioxide/Sc III complex as the catalyst. This protocol features broad substrate scope, high regio- and enantioselectivity, and good functional-group compatibility, providing a straightforward route to various trisubstituted allenes with a diarylphosphinate functionality in good yields with high enantioselectivities (up to 97 % yield, 96 % ee). Control experiments and theoretical calculations revealed that a synergistic effect of the counterion and water was critical for the regio- and enantioselective protonation after [1,2]-phospha-Brook rearrangement. The synthetic utility of this methodology was demonstrated by the conversion of products into complex bridged polycyclic architectures through intramolecular dearomatizing arene/allene cycloaddition., (© 2022 Wiley-VCH GmbH.)

Enantiopure monohydrosilanes are versatile chiral reagents for alcohol resolution and mechanistic investigation. Herein, we have demonstrated the asymmetric synthesis of monohydrosilanes via an intramolecular hydrosilylation strategy. This protocol is suitable for the synthesis of five- and six-membered cyclic monohydrosilanes, including a class of chiral oxasilacycles, with excellent diastereo-, regio-, and enantioselectivities. Notably, the catalyst loading could be reduced to 0.1 mol % which makes this one of the most efficient methods to access chiral monohydrosilanes. Mechanistic studies and DFT calculations indicate this Rh-catalyzed intramolecular asymmetric hydrosilylation reaction might proceed via a Chalk-Harrod mechanism, and the enantio-determining step was predicted to be oxidative addition of Si-H bond., (© 2021 Wiley-VCH GmbH.)

The regioselective and enantioselective synthesis of β-indolyl cyclopentenamides, a versatile chiral building block, by asymmetric addition of indoles to α,β-unsaturated iminium intermediates has been achieved through chiral anion catalysis. Key to the success of this methodology is the generation of a chiral anion-paired ketone-type α,β-unsaturated iminium intermediate from α-hydroxy enamides. Preliminary mechanistic studies and DFT calculations are consistent with a mechanism involving multiple, concurrent pathways for isomerization of the initially formed azaallylcation into the key α,β-unsaturated iminium intermediate, all mediated by the phosphoric acid catalyst., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanostructured oxides find multiple uses in a diverse range of applications including catalysis, energy storage, and environmental management, their higher surface areas, and, in some cases, electronic properties resulting in different physical properties from their bulk counterparts. Developing structure-property relations for these materials requires a determination of surface and subsurface structure. Although microscopy plays a critical role owing to the fact that the volumes sampled by such techniques may not be representative of the whole sample, complementary characterization methods are urgently required. We develop a simple nuclear magnetic resonance (NMR) strategy to detect the first few layers of a nanomaterial, demonstrating the approach with technologically relevant ceria nanoparticles. We show that the (17)O resonances arising from the first to third surface layer oxygen ions, hydroxyl sites, and oxygen species near vacancies can be distinguished from the oxygen ions in the bulk, with higher-frequency (17)O chemical shifts being observed for the lower coordinated surface sites. H2 (17)O can be used to selectively enrich surface sites, allowing only these particular active sites to be monitored in a chemical process. (17)O NMR spectra of thermally treated nanosized ceria clearly show how different oxygen species interconvert at elevated temperature. Density functional theory calculations confirm the assignments and reveal a strong dependence of chemical shift on the nature of the surface. These results open up new strategies for characterizing nanostructured oxides and their applications.