Visible-light-enabled stereoselective synthesis of functionalized cyclohexylamine derivatives via [4 + 2] cycloadditions.

An unprecedented intermolecular [4 + 2] cycloaddition of benzocyclobutylamines with α-substituted vinylketones, enabled by photoredox catalysis, has been developed. The current method enables facile access to highly functionalized cyclohexylamine derivatives that were otherwise inaccessible, in moderate to good yields with excellent diastereoselectivities. This protocol has some excellent features, such as full atom economy, good functional-group compatibility, mild reaction conditions, and an overall redox-neutral process. Additionally, an asymmetric version of this cycloaddition was preliminarily investigated via the incorporation of a chiral phosphoric acid (CPA), and moderate to good enantioselectivity could be effectively realized with excellent diastereoselectivity. Synthetic applications were demonstrated via a scale-up experiment and elaborations to access amino alcohol and cyclobutene derivatives. Based on the results of control experiments, a reasonable reaction mechanism was proposed to elucidate the reaction pathway.

Enantio- and Diastereoselective De Novo Synthesis of 3-Substituted Proline Derivatives via Cooperative Photoredox/Brønsted Acid Catalysis and Epimerization.

Herein, a novel strategy for the catalytic asymmetric synthesis of enantioenriched 3-cis- and 3-trans-substituted prolines has been successfully established via an unprecedented cascade radical addition/cyclization enabled by synergistic photoredox/Brønsted acid catalysis and subsequent base-assisted epimerization. The current protocol provides a unique de novo access to all four stereoisomers of 3-substituted prolines which are not readily achieved via currently established methods. This methodology could be further extended to the asymmetric synthesis of the full complement of stereoisomers of 3-substituted pipecolinic acids.

Trends of Ten Leading Causes of Death in Head and Neck Squamous Cell Carcinoma.

OBJECTIVE: An understanding of the leading causes of death in patients with head and neck squamous cell carcinoma (HNSCC) would be helpful to inform doctors, patients, and healthcare providers on disease management. This study aimed to comprehensively study the leading causes of death in these survivors. METHODS: We investigated the trends of risk factors for major causes of death in patients with HNSCC. Causes of death in HNSCC were obtained from the Surveillance, Epidemiology, and End Results registries. We characterized trends in the 5-year cumulative mortality as well as risk factors associated with the ten leading causes of death. RESULTS: Among 48 297 deaths identified, the ten leading causes were as follows: HNSCC, heart disease, lung cancer, chronic obstructive pulmonary disease (COPD), cerebrovascular disease, pneumonia & influenza, accidents & adverse effects, esophagus cancer, chronic liver diseases, and septicemia. Non-HNSCC deaths surpassed HNSCC deaths 4 years after cancer diagnosis. There was a significant decline in the 5-year cumulative mortality from HNSCC, heart disease, lung cancer, COPD, cerebrovascular disease, and esophagus cancer. The risks of mortality from the ten leading causes varied with patient characteristics. CONCLUSION: Our findings provide a useful picture of mortality patterns in HNSCC survivors, which might help when planning personalized HNSCC care.

Visible-Light-Enabled Enantioconvergent Synthesis of α-Amino Acid Derivatives via Synergistic Brønsted Acid/Photoredox Catalysis.

An unprecedented radical cross-coupling reaction was achieved between glycine esters and racemic α-bromoketones catalyzed by synergistic Brønsted acid/photoredox catalysis, thus serving as an efficient platform for the synthesis of highly valuable enantioenriched unnatural α-amino acid derivatives. This dual catalysis provides a powerful capability to control the reactive radical intermediate and iminium ion, thereby enabling enantioconvergent bond-formation in a highly stereochemical manner. An array of valuable enantioenriched unnatural α-amino acid derivatives bearing two contiguous stereogenic centers are readily accessible with high diastereoselectivity and excellent enantioselectivity, which include α-amino acids with a unique ß-fluorinated quaternary stereocenter or its ß-all-carbon counterpart. A strong chiral amplification effect was observed in this dual catalytic system.

Catalytic asymmetric de novo construction of dihydroquinazolinone scaffolds via enantioselective decarboxylative [4+2] cycloadditions.

The first de novo construction of enantioenriched dihydroquinazolinones via an intermolecular strategy has been established. This approach also represents the first catalytic asymmetric [4+2] cycloaddition of vinyl benzoxazinanones with sulfonyl isocyanates, which afforded chiral dihydroquinazolinones in high yields and excellent enantioselectivities (up to 98% yield, 99 : 1 er). This reaction not only confronts the great challenge in de novo construction of enantioenriched dihydroquinazolinone skeletons, but also advances the chemistry of decarboxylative cycloadditions involving vinyl benzoxazinanones.

Automatic localization of macular area based on structure label transfer.

AIM: To explore feasibility and practicability of macula localization independent of macular morphological features. METHODS: A novel method was proposed to identify macula in fundus images by using structure label transfer. Its main idea was to match a processed image with the candidate images with known structures, and then transfer the structure label representing the macular to the processed image as a result of macula localization. In this way, macula localization couldn't be influenced by lesion or other interference any more. RESULTS: The average success rate in four datasets was 98.18%. For accuracy, the average error distance in four datasets was 0.151 optic disc diameter (ODD). Even for severe lesion images, the proposed method can still maintain high success rate and high accuracy, e.g., 95.65% and 0.124 ODD in the case of STARE dataset, respectively, which indicated that the proposed method was highly robust and stable in the complicated situations. CONCLUSION: The proposed method can avoid the interference of lesion to macular morphological features in macula localization, and can locate macula with high accuracy and robustness, verifying its feasibility.

UV-Vis Spectrum Characteristics of Phycocyanin Purification in Water from Chao Lake.

Fresh blue algal from Chao Lake was used in this study. The crude extracts of phycocyanin were obtained with freeze-thaw method. The purification of phycocyanin was performed by combining two-step salt precipitation and two-step column chromatography. The reagent grade phycocyanin was achieved. Phycocyanin and impurity solution were obtained respectively in various stages subjected to the UV-Vis absorption spectrum scanning. With the development of the four-step purification process, the absorption peak of phycocyanin solution was redshifted from 260 to 280 nm in the wavelength range from 250 to 300 nm, and the maximum absorption peak of phycocyanin was redshifted from 617 to 620 nm in the wavelength range from 500nm to 700 nm. In the wavelength range from 250 to 700 nm, it showed that the impurity solution mainly contained impurity proteins and part of the phycocyanin in the first salting out, and mainly contained nucleic acids and vitamins substance in the second salting out. The first outflow components mainly contained phycoerythrin separated by the first column chromatography. The last outflow components mainly contained allophycocyanin separated by the second column chromatography. After the four-step purification process, the final purity of phycocyanin (A620/A280) is greater than 4,which met the standard of reagent grade．Thus it can be seen that two-step salt precipitation had a main function which was to remove impurity proteins, nucleic acids and vitamins substance, and two-step column chromatography main function was to remove phycoerythrin and allophycocyanin which were similar to phycocyanin.

Method for Aluminum Oxide Thin Films Prepared through Low Temperature Atomic Layer Deposition for Encapsulating Organic Electroluminescent Devices.

Preparation of dense alumina (Al2O3) thin film through atomic layer deposition (ALD) provides a pathway to achieve the encapsulation of organic light emitting devices (OLED). Unlike traditional ALD which is usually executed at higher reaction n temperatures that may affect the performance of OLED, this application discusses the development on preparation of ALD thin film at a low temperature. One concern of ALD is the suppressing effect of ambient temperature on uniformity of thin film. To mitigate this issue, the pumping time in each reaction cycle was increased during the preparation process, which removed reaction byproducts and inhibited the formation of vacancies. As a result, the obtained thin film had both high uniformity and density properties, which provided an excellent encapsulation performance. The results from microstructure morphology analysis, water vapor transmission rate, and lifetime test showed that the difference in uniformity between thin films prepared at low temperatures, with increased pumping time, and high temperatures was small and there was no obvious influence of increased pumping time on light emitting performance. Meanwhile, the permeability for water vapor of the thin film prepared at a low temperature was found to reach as low as 1.5 × 10-4 g/(m²·day) under ambient conditions of 25 °C and 60% relative humidity, indicating a potential extension in the lifetime for the OLED.