Asymmetric Intramolecular Hydroamination to Construct Diverse N-N/C-N Indole Atropisomers via Cooperative Pd(0) and Chiral Phosphoric Acid Catalysis.

Here we present an enantioselective intramolecular hydroamination reaction of -aminophenyl-1,3-enynes via cooperative catalysis of Pd(0) and chiral phosphoric acid. This approach enables the efficient construction of N-N/C-N axially stereogenic indoles with broad skeletal diversity and high levels of enantioselectivity in a completely atom-economic manner. Mechanistic studies indicate that a protonation of the alkyne moiety via Pd(0) π-Lewis base activation is favored, and the chiral phosphate counteranion plays a crucial role in controlling the atroposelectivity in the ring-closure step.

Palladium(0) and Brønsted Acid Co-Catalyzed Enantioselective Hydro-Cyclization of 2,4-Dienyl Hydrazones and Oximes.

The transition metal-catalyzed asymmetric hydro-functionalization of 1,3-dienes has been well explored, but most reactions focus on electron-neutral substrates in an intermolecular manner. Here we first demonstrate that readily available 2,4-dienyl hydrazones and oximes can be efficiently utilized in the hydro-cyclization reaction under co-catalysis of a Brønsted acid and a chiral palladium complex, furnishing multifunctional dihydropyrazones and dihydroisoxazoles, respectively. Diverse substitution patterns for both types of electron-deficient diene compounds are tolerated, and corresponding heterocycles were generally constructed with moderate to excellent enantioselectivity, which can be elaborated to access products with higher molecular complexity and diversity.

Asymmetric 2,4-Dienylation/[4 + 2] Annulation Cascade to Construct Fused Frameworks via Auto-Tandem Palladium Catalysis.

A palladium catalyzed tandem reaction between -functionalized aryl enones and 2,4-dienyl carbonates has been presented, proceeding through sequential 2,4-dienylation/Michael addition/π-σ-π isomerization/allylic alkylation. A broad array of enantioenriched architectures having fused and spirocyclic frameworks are constructed in moderate to excellent yields and stereoselectivity. Notably, the intrinsic intramolecular Diels-Alder reaction pattern of the dienylated intermediates is well reversed via Pd(0)-π-Lewis base catalysis.

Determination of Tear Lipid Film Thickness Based on a Reflected Placido Disk Tear Film Analyzer.

This study aims at determining the thickness of the tear lipid layer (LL) observed from a placido-disc-based tear film analyzer. We prospectively collected reflections of placido-disk LL images using a tear film analyzer (Keratograph 5M, Oculus) from subjects with dry eye symptoms. The LL thickness (LLT) over the inferior half of the cornea was estimated with the use of interference color analysis and the preprocessing of images with and without ring segmentation were obtained and analyzed.

Effects of melatonin on the nitric oxide system and protein nitration in the hypobaric hypoxic rat hippocampus.

Background: It is well documented that the nitric oxide (NO) might be directly involved in brain response to hypobaric hypoxia, and could contribute to memory deficiencies. Recent studies have shown that melatonin could attenuate hypoxia or ischemia-induced nerve injuries by decreasing the production of free radicals. The present study, using immunohistochemical and immunoblot methods, aimed to explore whether melatonin treatment may affect the expression of nitric oxide system and protein nitration, and provide neuroprotection in the rat hippocampus injured by hypobaric hypoxia.