نتایج جستجو برای: ugi four component
تعداد نتایج: 1200492 فیلتر نتایج به سال:
With the emergence of high-throughput screening in the pharmaceutical industry over a decade ago, synthetic chemists were faced with the challenge of preparing large collections of molecules to satisfy the demand for new screening compounds. The unique exploratory power of multicomponent reactions such as the Ugi four-component reaction was soon recognized to be extremely valuable to produce co...
We have synthesised a novel oxanorbornene β-aminoacid derivative and employed it in a stereoselective Ugi reaction. Hypothesis regarding the mechanism taking place during the reaction have been made and validated through the determination of the relative and absolute configuration of the Ugi adducts. Use of the correct choice of solvents can increase stereoselection. The resulting bicyclic pept...
A convenient base-mediated two-step synthesis of cotinine analogs and a one-pot base-free synthesis of iso-cotinine derivatives featuring an Ugi-4CR/cyclization protocol are reported. These approaches exploit the reactivity of the peptidyl position present in the Ugi adducts, allowing the facile construction of the γ-lactam core, as well as the introduction of a N-substituted methyl group into ...
This study assessed the screening rates for gastric cancer by two different screening methods, upper gastrointestinal (UGI) series and endoscopy; intentions to undergo future gastric cancer screening; and the preferred method of screening. The study population was derived from the 2006 Korean National Cancer Screening Survey. The Korean National Cancer Screening Survey is an annual cross-sectio...
The synthesis of nonsymmetrical polyamines (PAs) has, up to now, been problematic due to lengthy synthetic procedures, lack of regioselectivity, and very poor atom economy. An innovative synthetic protocol for nonsymmetrical PAs using a modified Ugi reaction ( N-split Ugi) which simplifies the synthesis of these tricky compounds is described. We believe that this new synthesis may open the door...
In recent years there have been significant advances in the field of Unsupervised Grammar Inference (UGI) for Natural Languages such as English or Dutch. This paper presents a broad range of UGI implementations, where we can begin to see how the theory has been put in to practise. Several mature systems are emerging, built using complex models and capable of deriving natural language grammatica...
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