Boronic chalcone

Figure 15.70). Boronic chalcones are reported to be antitumor agents (Figure 15.70). ... 

Boron trifluoride etherate, is also a good catalyst for this hydride transfer to chalcone. Unlike triphenylmethyl perchlorate, however, chalcone is able to enter Michael additions with the 1,5-diketone followed by eliminations leading to unexpected products, e.g., 3-benzyl-2,4,6-triphenylpyrylium from 2-carbethoxy-l,3,5-tri-phenylpentane-l,5-dione and chalcone the benzyl group originates from chalcone, the elimination product being ethyl benzoylacetate. ... 

Oxidation of chalcones with TTN has been studied in detail (95, 96), and it has been shown that the products obtained depend on the amount of reagent and the solvent employed. Oxidation with 1 equivalent of TTN in methanol, methanol-chloroform, or methanol-boron trifluoride leads to acetals of the type (XXXIV) (see also Scheme 21) in yields of 20-80%. When 3 equivalents of TTN are employed, however, and aqueous glyme containing a little perchloric acid used as solvent, the products are benzils. This remarkable transformation, which proceeds in yields varying from moderate to good (40-80%), involves three distinct oxidations by TTN, and these are outlined in Scheme 22. Each individual step in this reaction sequence has been investigated in detail, with the result that useful procedures have been developed for the oxidation of both deoxybenzoins and benzoins to benzils with TTN (96). 

The oxidative rearrangement of chalcones is a valuable route to isoflavones which has been thoroughly investigated. Initially, the conversion was achieved in two distinct steps. Epoxidation of a 2 -benzyloxychalcone, carried out by conventional techniques, is followed by treatment with a Lewis acid, such as boron trifluoride etherate, which brings about the rearrangement. 

The formation of a mixture of pyrylium salts when 2-acetylpyridine and chalcone reacted in perchloric acid was overcome by treating the reactants with ethanolic sodium hydroxide. The pentanedione was isolated and subsequently oxidized by reaction with chalcone and boron trifluoride (82JCS(P1)125). 

Boron heterocycles. A novel synthesis of the natural chalcone aurentiacin (3) involves the reaction of 2,4,6-trimethoxytoluene (1) with cinnamic acid and BF3 etherate at 80° to form the novel heterocycle 2, which is hydrolyzed to 3. The formation of 2 involves a selective demethylation, since the reaction of 4 with 2-phenylpropionic acid and BF3 followed by hydrolysis gives 5, isomeric with dihydro-3. 

Chart 8 Chemical structures of the CA4 boronic acid bioisostere (9) and of MDL-27048. The former was proposed by a structure-based molecular modeling study, the latter was used to elaborate a virtual screening protocol for the identification of novel chalcone CSI... 

If the alkyne in the second step is a 1-aryl propargyl alcohol the product is a bischalcone as a consequence of a CIR-CIR sequence. Furthermore, it is also possible to perform CIR-Heck and CIR-Suzuki sequences if alkenes or boronates and potassium carbonate are added after completion of the initial CIR step. Here again, the gradual differences in reactivity in the oxidative addition between an electron-deficient and an electro-neutral carbon-bromine bond can be readily exploited for selective cross-coupling, first to furnish an aryl propargyl alcohol that is slowly isomerized upon base catalysis to give the bromo chalcone for further cross-coupling. 

Ethyl acetoacetate reacts with chalcone in the presence of boron fluoride etherate affording 3-carbethoxy-2-methyl-4,6-diphenylpyryl-ium this can be hydrolyzed and decarboxylated to 2-methyl-4,6-diphenylpyryliumz79a which should theoretically result from acetone and chalcone. 

A solution of trans-chalcone oxide (fra s-l -benzoyl-2-phenyloxirane) (0.5 g) in anhydrous ether (25 ml) is heated at the b.p. with boron trifluoride etherate (5 ml) for 30 min. The mixture is then shaken with water and the a-formyldeoxybenzoin that is formed quantitatively is precipitated as copper salt. 

It is of interest to note in passing that In more recent work (ref.72), use has been made in synthesis of the transformation of chalcones to isoflavones with thallium(lll) nitrate. Thus, 6-acetyl-2,2-dimethyl-7-hydroxy-5-methoxychromanone was converted to the chalcone with 2,4-dibenzyloxybenzaldehyde. The O-acetyl derivative by treatment with the thallium reagent followed by acidic cyclisation gave a bischromanone structure. Selective reduction of the least hindered carbonyl group in the bischromanone, acidic dehydration of the resultant alcohol and final debenzylation with boron trichloride gave the linear isofiavone. 

Inexpensive di-, tri-, and tetramethoxyanthraquinones can be selectively dealkylated to hydroxymethoxyanthraquinones by the formation of difluoroboron chelates with BF3-OEt2 in benzene and subsequent hydrolysis with methanol. These un-symmetrically functionalized anthraquinone derivatives are useful intermediates for the synthesis of adriamycin, an antitumor agent. 2,4,6-Tiimethoxytoluene reacts with cinnamic acid and BF3-OEt2, with selective demethylation, to form a boron heterocycle which can be hydrolyzed to the chalcone aurentiacin (eq 34). 2 ... 

Lakowicz quickly recognized the importance of stilbene boronic acid 6d and has since prepared several analogous ICT fluorophore systems, including oxazoline 8 [45], chalcones 9a,b [46] and boron-dipyrromethene (BODIPY) 10 [47]. The observed stability constants (Kapp) for 8 were 526 for D-fructose and 27 for D-glucose in 2 1 (v/v) water-medianol at pH 7.0 (phosphate buffer). J< pp for 9a,b were 400, 476 M" for D-fructose and 29, 33 M" for D-glucose in 2 1 (v/v) water-methanol at pH 6.5 (phosphate buffer). K pp for 10 were 1000 for D-fructose and 13.7 M" for D-glucose in water at pH 7.5 (phosphate buffer). 

Discovery of a boronic acid analog of chalcone as a potent anticancer proliferation agent... 

Chalcones represent a class of natural products that can be readily synthesized in efforts to improve and optimize biological activities. In this study we designed and synthesized novel boronic acid analogs of chalcones. The cytotoxicity study identified a boronic acid chalcone YK-3-237 was potent towards 16 human cancer cell lines with GI50-values in the range of 10-200 nM, and another three cell lines with GI50-values below 10 nM. Both in vitro assay and cell cycle assay excluded the involvement of this compound in either assembly or disassembly process of tubulin. Furthermore, this... 

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