RESUMEN
Stereoselectively-fluorinated analogs of pipecolic acid have been investigated through a combined theoretical and experimental approach. Three of the four possible diastereoisomers of 4,5-difluoropipecolic acid were successfully synthesized via deoxyfluorination chemistry, navigating a complex reaction network that included neighboring group participation, rearrangement, and elimination pathways. A DFT-based conformational study, supported by NMR J-based analysis, revealed that the different diastereoisomers of 4,5-difluoropipecolic acid preferentially adopt different puckers of the six-membered ring. These findings could have future relevance for the conformational control of biologically active peptides.
Asunto(s)
Ácidos PipecólicosRESUMEN
We report for the first time that the imidate radical can be efficiently added to glycals to generate glycosyl radicals, based on which a general, toxic-reagent-free synthesis of C-glycosides of 2-deoxy-2-amino sugars has been developed. Complementary to previous strategies, the reaction is 1,2-trans-stereoselective and could use aryl alkenes as substrates. The late-stage functionalization and density functional theory calculations are reported.
Asunto(s)
Alquenos/química , Glicósidos/síntesis química , Glicósidos/química , Indicadores y Reactivos/química , Estructura Molecular , EstereoisomerismoRESUMEN
The aim of this meta-analysis was to evaluate the diagnostic value of 3D time-of-flight magnetic resonance angiography (3D-TOF-MRA) in trigeminal neuralgia (TN). Relevant studies were identified by computerized database searches supplemented by manual search strategies. The studies were included in accordance with stringent inclusion and exclusion criteria. Following a multistep screening process, high quality studies related to the diagnostic value of 3D-TOF-MRA in TN were selected for meta-analysis. Statistical analyses were conducted using Statistical Analysis Software (version 8.2; SAS Institute, Cary, NC, USA) and Meta Disc (version 1.4; Unit of Clinical Biostatistics, Ramon y Cajal Hospital, Madrid, Spain). For the present meta-analysis, we initially retrieved 95 studies from database searches. A total of 13 studies were eventually enrolled containing a combined total of 1084 TN patients. The meta-analysis results demonstrated that the sensitivity and specificity of the diagnostic value of 3D-TOF-MRA in TN were 95% (95% confidence interval [CI] 0.93-0.96) and 77% (95% CI 0.66-0.86), respectively. The pooled positive likelihood ratio and negative likelihood ratio were 2.72 (95% CI 1.81-4.09) and 0.08 (95% CI 0.06-0.12), respectively. The pooled diagnostic odds ratio of 3D-TOF-MRA in TN was 52.92 (95% CI 26.39-106.11), and the corresponding area under the curve in the summary receiver operating characteristic curve based on the 3D-TOF-MRA diagnostic image of observers was 0.9695 (standard error 0.0165). Our results suggest that 3D-TOF-MRA has excellent sensitivity and specificity as a diagnostic tool for TN, and that it can accurately identify neurovascular compression in TN patients.