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Silicon-stereogenic chiral organosilanes have found increasing applications in synthetic chemistry, medicinal chemistry, and materials science. In this context, various asymmetric catalytic methods have been established for the diverse synthesis of silicon-stereogenic silanes. In particular, asymmetric organocatalysis is emerging as an important and complementary synthetic tool for the enantioselective construction of silicon-stereocenters, along with the rapid development of chiral-metal catalyzed protocols. Its advent provides a powerful platform to achieve functionalized silicon-stereogenic organosilanes with structural diversity, and should lead to great development in chiral organosilicon chemistry. In this Tutorial Review, we highlight these latest achievements from two aspects: desymmetrizations of prochiral tetraorganosilanes and dynamic kinetic asymmetric transformations of racemic organosilanes by employing five organocatalytic activation modes. The advantages, limitations and synthetic value of each protocol, as well as the synthetic opportunities still open for further exploration, are also discussed. [ABSTRACT FROM AUTHOR]

A direct diastereoselective aldol reaction of cyclic or acyclic α‐azido ketones with α‐trifluoromethyl (CF3) pyruvate catalysed by DABCO is developed, which allowed the facile access of CF3‐containing multifunctional organoazides with vicinal tetrasubstituted carbons in good to high yields and diastereoselectivities. Moreover, phenylethynyl trifluoro‐ and difluoromethyl ketones are also viable substrates. Up to 50 % enantioselectivity could be obtained in the initial exploration of the catalytic asymmetric variant. [ABSTRACT FROM AUTHOR]

Azacycles such as indoles and tetrahydroquinolines are privileged structures in drug development. Reported here is an unprecedented regiodivergent intramolecular nucleophilic addition reaction of imines as a flexible approach to access N‐functionalized indoles and tetrahydroquinolines, by the control of reaction at the N‐terminus and C‐terminus, respectively. Using ketimines derived from 2‐(2‐nitroethyl)anilines with isatins or α‐ketoesters, the regioselective N‐attack reaction gives N‐functionalized indoles, while the catalytic enantioselective C‐attack reaction affords chiral tetrahydroquinolines featuring an α‐tetrasubstituted stereocenter. Mechanistic studies reveal that hydrogen‐bonding interactions may greatly facilitate such unusual N‐attack reactions of imines. The utility of this protocol is highlighted by the catalytic enantioselective formal synthesis of (−)‐psychotrimine, and the construction of various fused aza‐heterocycles. [ABSTRACT FROM AUTHOR]

We report the first highly enantioselective construction of silicon-stereocenters by asymmetric enamine catalysis. An unprecedented desymmetric intramolecular aldolization of prochiral siladials was thus developed for the facile access of multifunctional silicon-stereogenic silacycles in high to excellent enantioselectivity. With an enal moiety, these adducts could be readily elaborated for the diverse synthesis of silicon-stereogenic compounds, and for late-stage modification., (© 2023 Wiley-VCH GmbH.)

Azacycles such as indoles and tetrahydroquinolines are privileged structures in drug development. Reported here is an unprecedented regiodivergent intramolecular nucleophilic addition reaction of imines as a flexible approach to access N-functionalized indoles and tetrahydroquinolines, by the control of reaction at the N-terminus and C-terminus, respectively. Using ketimines derived from 2-(2-nitroethyl)anilines with isatins or α-ketoesters, the regioselective N-attack reaction gives N-functionalized indoles, while the catalytic enantioselective C-attack reaction affords chiral tetrahydroquinolines featuring an α-tetrasubstituted stereocenter. Mechanistic studies reveal that hydrogen-bonding interactions may greatly facilitate such unusual N-attack reactions of imines. The utility of this protocol is highlighted by the catalytic enantioselective formal synthesis of (-)-psychotrimine, and the construction of various fused aza-heterocycles., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: To evaluate the feasibility and short-term results of transcatheter aortic valve implantation (TAVI) using a new transcatheter valve., Methods: Twenty healthy adult sheep received general anesthesia. Under the guidance of X-ray and transthoracic echocardiography (TTE), the new anti-calcification transcatheter valve was released from delivery system and implanted at the level of native aortic annulus via left common carotid artery. Position and function of the new anti-calcification transcatheter valve were evaluated by angiography and TTE immediately after intervention. Thirty day survival rate of animals was obtained., Results: New transcatheter valves were implanted in all sheep. Fifteen sheep (75%) survived up to 30 days and post-operative examination showed that the transcatheter valve was in optimal position without migration and mitral valve impingement. The native coronary artery was patent in these animals. There was a slight paravalvular leak in 5 sheep. Postoperative echocardiography showed reflux percentage was significantly increased (P < 0.05) compared pre-intervention. Effective orifice area, aortic systolic pressure, diastolic aortic pressure, mean aortic pressure, left ventricular systolic pressure, left ventricular end diastolic pressure and heart rate were similar between post and pre-intervention (all P < 0.05). Five sheep died after TAVI within 30 days, including one fatal ventricular fibrillation occurred immediately after releasing the transcatheter valve and another sheep died of acute myocardial infarction due to left main coronary artery occlusion evidenced by angiography. Two sheep died of severe mitral regurgitation at 8 and 12 hours post-operation and one died of infective endocarditis at 26 days after intervention., Conclusion: Our favorable preliminary results showed that it was feasible to perform TAVI using the new transcatheter valve.

Aim: To observe the effects of urea on ECG and sodium currents of ventricular myocyte in mice., Methods: ECG and patch clamp techniques were used in the experiments, to record ECG of mice and sodium currents of ventricular myocyte in mice., Results: Urea could lead mice heart rate evidently slow down (P < 0.01) with concentration dependent. The heart rate were (556 +/- 29, 469 +/- 37, 378 +/- 48) b minT in low, middle, high groups respectively before using urea and (612 +/- 27, 615 +/- 23, 619 +/- 26) x min(-1) after. The conduction block arrhythmia was happened in middle and high groups. The sodium currents of ventricular myocyte in mice was inhibited by urea(P < 0.05). The sodium currents amplitude value were reduced to (7.32 +/- 0.68, 5.69 +/- 0.64, 4.58 +/- 0.57) nA after using urea in each group and were (8.76 +/- 0.91, 8.87 +/- 1.01, 8.77 +/- 0.96) nA before, submit concentration dependent., Conclusion: Urea can inhibit the sodium currents of ventricular myocyte in mice to make it happen conduction block arrhythmia.