Evolutionary relationships between seryl-histidine dipeptide and modern serine proteases from the analysis based on mass spectrometry and bioinformatics.

Seryl-histidine dipeptide (Ser-His) has been recognized as the shortest peptide with hydrolysis cleavage activity; however, its protein cleavage spectrum has not yet been fully explored. Here, four differently folded proteins were treated with Ser-His, and the digestion products were evaluated with high-resolution mass spectrometry. The cleavage efficiency and cleavage propensity of Ser-His against these protein substrates were calculated at both the primary and secondary sequence levels. The above experiments show that Ser-His cleaves a broad spectrum of substrate proteins of varying secondary structures. Moreover, Ser-His could cleave at all 20 amino acids with different efficiencies according to the protein, which means that Ser-His has the original digestion function of serine proteases. Furthermore, we collected and compared the catalytic sites and cleavage sites of 340 extant serine proteases derived from 17 representative organisms. A consensus motif Ser-[X]-His was identified as the major pattern at the catalytic sites of serine proteases from all of the organisms represented except Danio rerio, which uses Ser-Lys instead. This finding indicates that Ser-His is the core component of the serine protease catalytic site. Moreover, our analysis revealed that the cleavage sites of modern serine proteases have become more specific over the evolutionary history of this family. Based on the above analysis results, it could be found that Ser-His is likely the original serine protease and maybe the evolutionary core of modern serine proteases.

Gold-catalyzed tandem cycloisomerization/functionalization of in situ generated α-oxo gold carbenes in water.

A gold-catalyzed tandem cycloisomerization/functionalization of in situ generated α-oxo gold carbenes in water has been developed, which provides ready access to highly functionalized indole derivatives from o-alkynyl anilines and ynamides. Importantly, gold serves dual catalytic roles to mediate both the cycloisomerization of o-alkynyl anilines and the intermolecular oxidation of ynamides at the same time, thus providing a new type of concurrent tandem catalysis. The use of readily available starting materials, a simple procedure, and mild reaction conditions are other notable features of this method.

Synthesis of Enantioenriched Pyrrolidines via Gold-Catalyzed Tandem Cycloisomerization/Hydrogenation of Chiral Homopropargyl Sulfonamides.

A novel gold-catalyzed tandem cycloisomerization/hydrogenation of chiral homopropargyl sulfonamides has been developed. Various enantioenriched pyrrolidines can be obtained in excellent yields and excellent enantioselectivities by combination of chiral tert-butylsulfinimine chemistry with gold catalysis. Importantly, this represents the first example of a pyrrolidine synthesis from homopropargyl sulfonamide.

Efficient and practical synthesis of enantioenriched 2,3-dihydropyrroles through gold-catalyzed anti-Markovnikov hydroamination of chiral homopropargyl sulfonamides.

A direct gold-catalyzed 5-endo-dig cycloisomerization of chiral homopropargyl sulfonamides has been developed. A range of enantioenriched 2,3-dihydropyrroles are readily accessed by utilizing this approach. Importantly, this gold-catalyzed cycloisomerization reaction proceeds through an anti-Markovnikov addition by using a catalytic base as the additive, which completely suppresses the undesired dimerization.

Atom-economic generation of gold carbenes: gold-catalyzed formal [3+2] cycloaddition between ynamides and isoxazoles.

The generation of gold carbenes via the gold-catalyzed intermolecular reaction of nucleophiles containing relatively labile N-O or N-N bonds with alkynes has received considerable attention during recent years. However, this protocol is not atom-economic as the reaction produces a stoichiometric amount of pyridine or quinoline waste, the cleaved part of the N-O or N-N bonds. In this article, we disclose an unprecedented gold-catalyzed formal [3+2] cycloaddition between ynamides and isoxazoles, allowing rapid and practical access to a wide range of synthetically-useful 2-aminopyrroles. Most importantly, mechanistic studies and theoretical calculations revealed that this reaction presumably proceeds via an α-imino gold carbene pathway, thus providing a strategically novel, atom-economic route to the generation of gold carbenes. Other significant features of this approach include the use of readily-available starting materials, high flexibility, simple procedure, mild reaction conditions, and in particular, no need to exclude moisture or air ("open flask").

Practical, modular, and general synthesis of 3-coumaranones through gold-catalyzed intermolecular alkyne oxidation strategy.

A gold-catalyzed intermolecular alkyne oxidation for the preparation of 3-coumaranones has been developed. Using 8-isopropylquinoline N-oxides as oxidants, the reactions of o-ethynylanisoles afford versatile 3-coumaranones in moderate to good isolated yields. The synthetic utility of this chemistry is also indicated by the synthesis of the natural product sulfuretin.

Gold-catalyzed intermolecular oxidation of chiral homopropargyl sulfonamides: a reliable access to enantioenriched pyrrolidin-3-ones.

A gold-catalyzed intermolecular oxidation of chiral homopropargyl sulfonamides has been developed, which provides a reliable access to synthetically useful chiral pyrrolidin-3-ones with excellent ee, by combining the chiral tert-butylsulfinimine chemistry and gold catalysis. This methodology has also been used in the facile synthesis of natural product (-)-irniine. The use of readily available starting materials, a broad substrate scope, a simple procedure and the mild nature of this reaction render it a viable alternative for the synthesis of enantioenriched pyrrolidin-3-ones.

Gold-catalyzed intermolecular oxidation of o-alkynylbiaryls: an easy and practical access to functionalized fluorenes.

A novel gold-catalyzed intermolecular oxidation of o-alkynylbiaryls has been developed. A variety of functionalized fluorenes are readily accessed by utilizing this non-diazo approach, thus providing a viable alternative to synthetically useful fluorenes.

Flexible and practical synthesis of 3-oxyindoles through gold-catalyzed intermolecular oxidation of o-ethynylanilines.

A novel gold-catalyzed intermolecular oxidation of o-ethynylanilines has been developed. A range of functionalized 3-oxyindoles are readily accessed by utilizing this strategy. Importantly, this gold-catalyzed oxidative process outcompetes the typical indole formation.

The utilization status of aspirin for the secondary prevention of ischemic stroke.

BACKGROUND: The present study was aimed to investigate the usage of aspirin for the secondary prevention of ischemic stroke, evaluate the correlated factors, and analyze the reasons for not taking and irregularly taking aspirin. METHODS: The patients in this group were all stroke survivors who have formerly been diagnosed with a cerebral infarction or transient ischemic attack (TIA) in our hospital. We investigated their use of aspirin over a three-year period following their hospitalization. According to the patients' aspirin usage, they were divided into treatment and non-treatment groups. In addition, the reasons for not taking or irregularly taking aspirin were analyzed in the two groups. RESULTS: A total of 1240 patients were studied, including 367 (29.60%) in the treatment group and 873 (70.40%) cases in the non-treatment group. In addition, 201 (16.20%) cases in the treatment group had been regularly taking aspirin (50 - 325 mg of aspirin daily) for 1 to 3 years or longer. The results demonstrated that the main reasons for not taking aspirin in this study were related to patients' concerns regarding the side effects of taking aspirin (46.45%), as well as the doctors' inadequacy in informing their patients to take aspirin (38.71%). The major reasons for patients to irregularly take aspirin were that the doctors did not notify the length of aspirin usage to their patients (41.57%), and that doctors did not prescribe aspirin upon the patients' follow-up visit (26.51%). CONCLUSION: The most effective way to increase patient's compliance for aspirin consumption is to promote the guidelines for stroke treatment and to relay these advances in stroke therapy to the patient.