This work was supported by the Foundation for Science and Technology (FCT), Portugal (projects PTDC/QUI-QUI/113687/2009 and PEst-C/QUI/UI0081/2013). A.G. (SFRH/BD/43531/2008) and M.J.M. (SFRH/BD/61262/2009) thank FCT for grants.

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Chromone: A Valid Scaffold in Medicinal Chemistry

Chromones as a privileged scaffold in drug discovery: a review.

While tremendous advances have been made in asymmetric synthesis, the resolution of racemates is still the most important industrial approach to the synthesis of chiral compounds. The use of enzymes for the kinetic resolution (KR) of racemic substrates to afford enantiopure compounds in high enantioselectivity and good yield has long been a popular strategy in synthesis. However, transition metal-mediated and more recently organocatalyzed KRs have gained popularity within the synthetic community over the last two decades due to the progress made in the development of chiral catalysts for asymmetric reactions. Many catalytic non-enzymatic procedures have been developed providing high enantioselectivity and yield for both products and recovered starting materials. Indeed, the non-enzymatic KR of racemic compounds based on the use of a chiral catalyst is presently an area of great importance in asymmetric organic synthesis. The goal of this review is to provide an update on the principal developments of catalytic non-enzymatic KR covering the literature since 2004. This review is subdivided into seven sections, according to the different types of compounds that have been resolved through catalytic non-enzymatic KR, such as alcohols, epoxides, amines, alkenes, carbonyl derivatives, sulfur compounds and ferrocenes.



Abbreviations: Ac: acetyl; acac: acetylacetone; AQN: anthraquinone; Ar: aryl; Atm: atmosphere; BINAM: 1,1′-binaphthalenyl-2,2′-diamine; BINAP: 2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl; BINEPINE: phenylbinaphthophosphepine; BINOL: 1,1′-bi-2-naphthol; Bmim: 1-butyl-3-methylimidazolium; Bn: benzyl; Boc: tert-butoxycarbonyl; Box: bisoxazoline; BSA: bis(trimethylsilyl)acetamide; Bu: butyl; Bz: benzoyl; c: cyclo; CBS: Corey–Bakshi–Shibata; Cbz: benzyloxycarbonyl; COD: cyclooctadiene; COE: cyclooctene; Cy: cyclohexyl; Dba: (E,E)-dibenzylideneacetone; DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene; DCC: N,N′-dicyclohexylcarbodiimide; de: diastereomeric excess; DEAD: diethyl azodicarboxylate; Dec: decanyl; DHQD: dihydroquinidine; Difluorphos: 5,5′-bis(diphenylphosphino)-2,2,2′,2′-tetrafluoro-4,4′-bi-1,3-benzodioxole; DIPEA: diisopropylethylamine: DKR: dynamic kinetic resolution; DMAP: 4-dimethylaminopyridine; DMSO: dimethyl sulfoxide; DNA: deoxyribonucleic acid; DOSP: N-(dodecylbenzenesulfonyl)prolinate; DTBM: di-tert-butylmethoxy; ee: enantiomeric excess; Et: ethyl; equiv.: equivalent; Fu: furyl; Hex: hexyl; HIV: human immunodeficiency virus; HMDS: hexamethyldisilazide; KR: kinetic resolution; L: ligand; LDA: lithium diisopropylamide; MAO: methylaluminoxane; Me: methyl; Ms: mesyl; MTBE: methyl tert-butyl ether; Naph: naphthyl; nbd: norbornadiene; NBS: N-bromosuccinimide; NIS: N-iodosuccinimide; Pent: pentyl; Ph: phenyl; Piv: pivaloyl; PMB: p-methoxybenzoyl; Pr: propyl Py: pyridyl; r.t.: room temperature; s: selectivity factor; Segphos: 5,5′-bis(diphenylphosphino)-4,4′-bi-1,3-benzodioxole; (S,S′,R,R′)-Tangphos: (1S,1S′,2R,2R′)-1,1′-di-tert-butyl-(2,2′)-diphospholane; TBS: tert-butyldimethylsilyl; TBDPS: tert-butyldiphenylsilyl; TCCA: trichloroisocyanuric acid ; TEA: triethylamine; TEMPO: tetramethylpentahydropyridine oxide; THF: tetrahydrofuran; Thio: thiophene; Tf: trifluoromethanesulfonyl; TMS: trimethylsilyl; Tol: tolyl; Ts: 4-toluenesulfonyl (tosyl)

Catalytic Non-Enzymatic Kinetic Resolution

The balance between bone resorption and bone formation is vital for maintenance and regeneration of alveolar bone and supporting structures around teeth and dental implants. Tissue regeneration in the oral cavity is regulated by multiple cell types, signaling mechanisms, and matrix interactions. A goal for periodontal tissue engineering/regenerative medicine is to restore oral soft and hard tissues through cell, scaffold, and/or signaling approaches to functional and aesthetic oral tissues. Bony defects in the oral cavity can vary significantly, ranging from smaller intrabony lesions resulting from periodontal or peri-implant diseases to large osseous defects that extend through the jaws as a result of trauma, tumor resection, or congenital defects. The disparity in size and location of these alveolar defects is compounded further by patient-specific and environmental factors that contribute to the challenges in periodontal regeneration, peri-implant tissue regeneration, and alveolar ridge reconstruction. Efforts have been made over the last few decades to produce reliable and predictable methods to stimulate bone regeneration in alveolar bone defects. Tissue engineering/regenerative medicine provide new avenues to enhance tissue regeneration by introducing bioactive models or constructing patient-specific substitutes. This review presents an overview of therapies (e.g., protein, gene, and cell based) and biomaterials (e.g., resorbable, nonresorbable, and 3-dimensionally printed) used for alveolar bone engineering around teeth and implants and for implant site development, with emphasis on most recent findings and future directions.

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Regenerative Medicine for Periodontal and Peri-implant Diseases

The isoxazolidine ring represents one of the privileged structures in medicinal chemistry, and there have been an increasing number of studies on isoxazolidine and isoxazolidine-containing compounds. Optimization of the 1,3-dipolar cycloaddition (1,3-DC), original methods including electrophilic or palladium-mediated cyclization of unsaturated hydroxylamine, has been developed to obtain isoxazolidines. Novel reactions involving the isoxazolidine ring have been highlighted to accomplish total synthesis or to obtain bioactive compounds, one of the most significant examples being probably the thermic ring contraction applied to the total synthesis of (±)-Gelsemoxonine. The unique isoxazolidine scaffold also exhibits an impressive potential as a mimic of nucleosides, carbohydrates, PNA, amino acids, and steroid analogs. This review aims to be a comprehensive and general summary of the different isoxazolidine syntheses, their use as starting building blocks for the preparation of natural compounds, and their m...

Isoxazolidine: A Privileged Scaffold for Organic and Medicinal Chemistry

Investigations on Regio‐ and Stereoselectivities in Cycloadditions Involving α‐(3‐Pyridyl)‐N‐phenylnitrone: Development of an Efficient Route to Novel Nicotine Analogues.

The purpose of this study was to compare Physical Fitness levels among 200, 500 and 1000 Meter Canoeing Players. To obtain data, the investigators had selected Twenty one (N = 21) male Canoeing Player of 19 to 25 years (Mean ± SD: Age: 19.761 ± 2.488 years; Body Mass: 1.749 ± 7.046 kilograms; Body Height: 65.047 ± 9.286 meters) of age to act as subjects. Components of Physical fitness (i.e., Agility, Balance, Coordination, Power, Reaction Time and Speed) were taken up for the present study. Statistical analysis was performed using the Statistical Package for the Social Sciences for Windows version 16.0 software (SPSS Inc., Chicago, IL). Data is expressed as the mean ± SD. One way Analysis of Variance (ANOVA) was employed to find out the intra-group differences. To test the hypothesis, the level of significance was set at 0.05. No significant differences were found in Agility, Balance, Coordination, Power and Speed. However, significant differences were found in Reaction Time. Article visualizations:

Physical fitness levels among 200, 500 and 1000 meter canoeing players: a comparative study

Substituted 3-formylchromones react with 2-phenyl-4-dimethylamino-1-thia-3-azabuta-1,3-diene ( 4 ) or thio-benzamide ( 7 ) by heating their toluene solution in a sealed tube to give novel substituted 3-(5-phenyl-3 H -[1,2,4]dithiazol-3-yl)chromen-4-ones ( 6a – e ) in high yields.

Unusual Conversion of Substituted‐3‐formylchromones to 3‐(5‐Phenyl‐3H‐[1,2,4]dithiazol‐3‐yl)chromen‐4‐ones: A Facile and Efficient Route to Novel 1,2,4‐Dithiazoles.

Abstract: Shied Metal Arc Welding is one of the most important joining processes in the industry. This type of welding is widely used in many areas like from industries to household in joining simple metal piece it mostly used due to its compatibility and cheap equipment’s cost because it due not require gas for shielding and its electrodes are also cheap. There are numerous studies and researches done around the world to understand geometry of SMAW welding under different operating conditions. Experiments are done considering various parameters of welding such as welding current, welding speed, welding voltage, welder skills etc. This helps in better acknowledgement of bead geometry of SMAW welding for maximum enhancement in various industries. in this research paper we have carried out an experiment on bead geometry of SMAW with varying current. After that we calculate the variation on the height of the reinforcement, depth of the penetration, width of the heat affected zone and the welded zone. In the experimental analysis, it is found that all the process parameter’s significantly affect the quality. The results revealed that the use of the optimum welding current parameters resulted in the improvements in the welded joint.

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Effects of Variation in Welding Current During SMAW Process on A36 Mild Steel

In contrast to the reported facile intramolecular 1,3-dipolar cycloadditions of in-situ generated nitrone on heterocyclic systems, reactions of 2-(N-allyl/crotyl/cinnamyl-anilino)-3-formylchromones with N-phenyl-/methylhydroxylamine under comparable conditions, afford fused isoxazolidines only in low to moderate yields; the corresponding amides derived from rearrangement of in situ generated nitrones are formed as major products. However, when reactions were carried by stirring the reactants at an ice-cold temperature in dichloromethane, highly stereoselective intramolecular 1,3-dipolar cycloadditions lead to novel fused isoxazolidines in high yields (80–90%).

Gurpinder Singh

Papers

Investigations on Regio‐ and Stereoselectivities in Cycloadditions Involving α‐(3‐Pyridyl)‐N‐phenylnitrone: Development of an Efficient Route to Novel Nicotine Analogues.

Physical fitness levels among 200, 500 and 1000 meter canoeing players: a comparative study

Unusual Conversion of Substituted‐3‐formylchromones to 3‐(5‐Phenyl‐3H‐[1,2,4]dithiazol‐3‐yl)chromen‐4‐ones: A Facile and Efficient Route to Novel 1,2,4‐Dithiazoles.

Effects of Variation in Welding Current During SMAW Process on A36 Mild Steel

Intramolecular Low-Temperature 1,3-Dipolar Cycloadditions of Nitrones: Synthesis of Chromano-Heterocycles.