Chalcones activity

Disubstituted flavanones and chromanones are produced with good enantioselectivity from chalcones activated by an a-fert-butyl ester function through an intramolecular Michael addition catalysed by a chiral thiourea derivative. In situ decarboxylation enhances the ee and yields remain high <07JA3830>. A comprehensive study of the asymmetric cyclisation of 2 -hydroxychalcones to flavanones has refuted the ability of camphorsulfonic acid to achieve enantioselectivity but has shown that cinchona-based catalysts can be effective <07EJO5886>. 

The reactions of TTN with a variety of unsaturated systems have been studied systematically during the last two years, and the results obtained clearly establish the synthetic utility of the reagent as a specific oxidant. Attempts were made in 1966 by Uemura et al. 162) to oxidize a,)8-unsatur-ated carbonyl compounds with thallium(III) acetate, but were unsuccessful. In 1970, however, Ollis and his co-workers 121-123) reported that prolonged treatment of highly activated chalcones (Scheme 20) with thal-... 

Table 3 summarizes the scope and limitation of substrates for this hydrogenation. Complex 5 acts as a highly effective catalyst for functionalized olefins with unprotected amines (the order of activity tertiary > secondary primary), ethers, esters, fluorinated aryl groups, and others [27, 30]. However, in contrast to the reduction of a,p-unsaturated esters decomposition of 5 was observed when a,p-unsaturated ketones (e.g., trans-chalcone, trans-4-hexen-3-one, tra s-4-phenyl-3-buten-2-one, 2-cyclohexanone, carvone) were used (Fig. 3) [30],... 

Brown T, Holt H Jr, Lee M (2006) Synthesis of Biologically Active Heterocyclic StUbene and Chalcone Analogs of Combretastatin. 2 1-51... 

A series of chiral p-hydroxysulfoximine ligands have been synthesised by Bolm et al. and further investigated for the enantioselective conjugate addition of ZnEt2 to various chalcone derivatives. The most eiScient sulfoximine, depicted in Scheme 2.33, has allowed an enantioselectivity of up to 72% ee to be obtained. These authors assumed a nonmonomeric nature of the active species in solution, as suggested by the asymmetric amplification in the catalysis with a sulfoximine of a low optical purity. 

R. Edenharder, 1. von Petersdorff, and R. Rauscher, Antimutagenic effects of flavonoids, chalcones and structurally related compounds on the activity of 2-amino-3-methylimidazo(4,5-f quinoline (IQ) and other heterocyclic amine mutagens from cooked food. Mutat Res. 287 261 (1993). 

Chalcones Chemical library probed with pharmacophore Ligands active in vitro and in vivo [118]... 

Licochalcone (50) is a natural product that is isolated from the roots of Chinese liquorice and is reported to have antileishmanial activity [49]. A series of chromene-substituted chalcones related to licochalcone have been reported to have antileishmanial activity [50]. Compound 51 was reported to have an IC50 of 1.2 pM against Leishmania major promastigotes versus meglumine antimoniate (IC50 =30 pM). Various compounds related to 51 have potent antileishmanial activity (IC50 < 3 pM) with potency similar to 51, but they did not show cytotoxicity. 

The readily prepared support was then used for dihydropyrimidine and chalcone synthesis (Scheme 7.29). Thus, the modified support was activated prior to reaction by treatment with tosyl chloride. Solutions of the appropriate acetophenones were then spotted onto the membrane and the support was submitted to microwave irradiation for 10 min [45]. In the next step, several aryl aldehydes were attached under microwave irradiation to form a set of corresponding chalcones through a Claisen-Schmidt condensation. 

Similarly, Scheme 44 indicates that Selvan et al. utilized -hydroxy enones (e.g., 169) to synthesize pyrazoles (e.g., 170) [87]. Although this example is a cur cumin analog and not a chalcone derivative, it has been included as this class of compounds exhibited anti-oxidant and COX-l/COX-2 activity. 

Isoxazolines are partially unsaturated isoxazoles. In most cases these compounds are precursors to the isoxazoles, and as a result, the synthesis can also be found in Sect. 3.2.1b. Kaffy et al., used a 1,3-dipolar cycloaddition of a nitrile oxide (186) with the respective styrene (201a or b) to generate isoxazolines (202a or b, respectively). Depending on the substitution of the vinyl portion of the styrene molecule, either 3- or 4-substituted isoxazolines could be formed (Scheme 55) [94], Simoni et al. employed similar chemistry to produce isoxazolines [60]. Kidwai and Misra emplyed microwave technology to treat chalcones with hydroxylamine and basic alumina [99]. The isoxazoles synthesized by Simoni et al. possess anti-proliferative and apoptotic activity in the micromolar range [60]. 

In this chapter, we describe the atomic resolution structural elucidation of several plant type III polyketide synthases, including chalcone synthase, 2-pyrone synthase, and stilbene synthase. Manipulation of the catalytic activity and specificity of these biosynthetic enzymes by using a structurally guided approach offers a novel... 

CHS orchestrates the condensation, cyclization, and aromatization of one p-coumaroyl-CoA and three malonyl-CoA molecules to produce chalcone (Fig. 12.2).22 Transfer of the p-coumaroyl moiety from the CoA-linked starter molecule to Cys 164 within the active site initiates the reaction sequence. Next, the sequential condensation of three acetate units, derived from malonyl-CoA, with the enzyme-bound coumaroyl moiety forms a tetraketide intermediate. Inherent in the condensation reaction is decarboxylation of malonyl-CoA to an acetyl-CoA carbanion that serves as a nucleophile during the successive chain elongation... 

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