نتایج جستجو برای: modal auxiliaries

تعداد نتایج: 38440  

Journal: :The Journal of Contemporary Dental Practice 2001

Abstract Task-based language teaching is considered an effective way to achieve a harmony between grammar and communication. The present study investigates two different ways of teaching modal verbs: task-based versus traditional approaches. To this purpose, an Oxford Placement Test was administered to select 40 homogeneous participants out of a larger population who took this test. The selecte...

Journal: :Chemical communications 2012
Jochem P A Rutters Yvette Verdonk Remko de Vries Steen Ingemann Henk Hiemstra Vincent Levacher Jan H van Maarseveen

A new method is presented to prepare strained lactams. Esterification of the C-terminus of a dipeptide with β-nitrostyrene or quinoline-type auxiliaries is followed by lactam formation by an intramolecular aza-Michael-acyl-transfer reaction cascade. Ultimately, the cyclic tetrapeptide cyclo[Phe-Tyr-Ala-Gly] has been prepared.

Journal: :Molecules 2014
Gaspar Diaz Michelle A A de Freitas Maria E Ricci-Silva Marisa A N Diaz

An interesting new approach was developed for the synthesis of Evans' chiral auxiliaries with excellent yields. In turn, another new stereoselective and efficient strategy has also allowed for the preparation of a 2-oxazolidinone derivative in 34% overall yield from the Morita-Baylis-Hillman adduct. The antibacterial activity of this oxazolidinone was tested against Staphylococcus aureus strain...

Journal: :Molecules 2017
Jeyun Jo Seok-Ho Kim Young Taek Han Jae-Hwan Kwak Hwayoung Yun

Asymmetric synthesis of naturally occurring diverse ring systems is an ongoing and challenging research topic. A large variety of remarkable reactions utilizing chiral substrates, auxiliaries, reagents, and catalysts have been intensively investigated. This review specifically describes recent advances in successful asymmetric cyclization reactions to generate cyclic architectures of various na...

Journal: :Chemical communications 2013
John D Knight Don M Coltart

The asymmetric anti-aldol addition of ketone-derived donors and aldehyde acceptors is described. Asymmetric induction is achieved through the use of chiral N-amino cyclic carbamate (ACC) auxiliaries. The transformation exhibits essentially perfect anti-diastereoselectivity and enantioselectivity, and has the unusual feature of proceeding via thermodynamic, rather than kinetic control.

In this paper, a computationally simple approach for damage localization and quantification in beam-like structures is proposed. This method is based on using modal flexibility curvature (MFC) and particle swarm optimization (PSO) algorithm. Analytical studies in the literature have shown that changes in the modal flexibility curvature can be considered as a sensitive and suitable criterion for...

2013
András Imrényi

This paper addresses a hot topic of Hungarian syntactic research, viz. the treatment of “discontinuous” constructions involving auxiliaries. The case is made for a projective dependency grammar (DG) account built on the notions of rising and catenae (Groß and Osborne, 2009). Additionally, the semantic basis of the dependency created by rising is described with a view to analogy and construction...

Journal: :Molecules 2011
Xuefeng Jia Aijun Lin Zhijie Mao Chengjian Zhu Yixiang Cheng

Chiral C₂-symmetric diamines have emerged as versatile auxiliaries or ligands in numerous asymmetric transformations. Chiral 2,2'-bispyrrolidine-based salan ligands were prepared and applied to the asymmetric aryl transfer to aldehydes with arylboronic acids as the source of transferable aryl groups. The corresponding diarylmethanols were obtained in high yields with moderate to good enantiosel...

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