Coumarin skeleton

The first systems without anomalous fluorescence discussed in the context of TICT states were coumarine laser dyes. Jones and coworkers208210 demonstrated that dialkylaminocoumarines like 7C showed an increase of the nonradiative decay rate in strongly polar solvents. This effect is dramatically increased if the acceptor properties of the coumarine skeleton are stronger, for example, in F7C. On the other... 

A Michael Addition leads to the formation of the coumarin skeleton. This addition is followed by rearomatisation ... 

Abstract Construction of chemical libraries is a useful approach to the discovery of better fluorescent materials, and several types, such as styryl dyes and cyanine dyes, have been reported. In this chapter, we focus on construction of a library of chemicals having a coumarin skeleton as the core structure. Coumarin and its derivatives are key structures in various bioactive or fluorescent molecules, and their fluorescence properties are dependent on the precise structure, including the positions of substituents. 

The molecular formula and collective NMR data for compound 12 seemed to fit nicely into the structure of the isochromenone, orthosporin, which was previously reported from the fungus Rhynchosporium orthosporum [109]. More careful comparison of the data, however, indicated that 12 fit into a coumarin skeleton, as shown in Fig. (3). There are few 3-alkyl- 6,8-dioxy coumarins known from fungal sources. These include 3-hydroxy-methyl-6,8-dimethoxy coumarin from Talaromyces flavus [110]. 

Catalytic methods of creation and functionalization of the coumarin skeleton 12KGS175. 

Retrosynthetic analysis of the target coumarin skeleton provides two major synthetic routes (Figure 10.1). Route A requires an aromatic o-hydroxy carbonyl compound and a two-carbon fragment observed in Knoevenagel and Perkin reactions reflecting the [4h-2] approach for the construction of six-membered heterocycles. Route B represents the reaction between phenols and three carbon fragments associated with the Pechmann cyclization. In recent years, newer synthetic methodologies have also been applied to the synthesis of a variety of coumarins that have avoided the use of concentrated sulfuric acid. The present chapter reviews various... 

B. Karimi and H. Behzadnia pubhshed the preparation of coumarins using PMSCl (7 mol%) with 2DP6mm hexagonal structure under solvent-free conditions at 130°C. Proposed mechanism for this reaction is demonstrated in (Scheme 22). The transesterification of the phenol and EAA in the presence of PMSCl as a Lewis acid catalyst generates species 33. Alternatively, Michael addition reaction creates a new ring to afford species 34. Rearomatization leads to the formation of the coumarin skeleton 35. Final-phase PMSCl is regenerated by dehydration (11CCAOAC1432). 

Structurally related to furocoumarins are the so-called coumestans, which contain a benzofuro[3,2-c]coumarin skeleton (Figure 2). The coumestans are found in a variety of plant species that are commonly used in traditional medicine and exhibit also a broad range of biological activities [25-27]. The group comprises hxmdreds of molecules with... 

Based on the preliminary understanding of ICT mechanism of coumarin core skeleton, the first systematic application of combinatorial approach toward the field of fluorescence chemistry was reported by Bauerle and co-workers in 2001 [44]. In their study, the structure-photophysical property relationships (SPR) of coumarin fluorophore were revealed by means of a combinatorial approach. 

Simple phenolic compounds include (1) the phenylpropanoids, trans-cinnamic acid, p-coumaric acid and their derivatives (2) the phenylpropanoid lactones called coumarins (Fig. 3.4) and (3) benzoic acid derivatives in which two carbons have been cleaved from the three carbon side chain (Fig. 3.2). More complex molecules are elaborated by additions to these basic carbon skeletons. For example, the addition of quinic acid to caffeic acid produces chlorogenic acid, which accumulates in cut lettuce and contributes to tissue browning (Fig. 3.5). 

A new class of secondary metabolites tyrolobibenzyls A 36 and B 37 were isolated from Scorzonera humilis (Asteraceae) of Tyrolean origin. Compounds 36 and 37 were shown to possess a unique phenylethylbenzofuran skeleton <00HCA292O>. The structure of the dimeric coumarin 38 was confirmed by an X-ray diffraction study, as well as by a photochemical synthesis from its co-occurring monomer bergapten <00H(53)441>. 

Coumarins also have a C6-C3 skeleton, but they possess an oxygen heterocycle as part of the C3-unit. There are numerous coumarins, many of which play a role in disease and pest resistance, as well as UV-tolerance. The coumarin umbelliferone (1.21) is popular in enzyme assays. Umbelliferone esters can be used as a substrate for non-specific esterase enzyme assays and in fluorescent immunoassays (Jacks and Kircher, 1967). In order to quantify the enzyme activity of the popular reporter gene P-glucuronidase (GUS), plant extracts can be incubated with 4-methylumbelliferyl P-D-glucuronide (4-MUG 1.22), which upon hydrolysis... 

Both contain the carbon-oxygen skeleton of coumarin. 

Transition from a chromenoid skeleton to a benzofuran has also been achieved by other means. We may mention the photooxidation of rotenone and the preparation of 5,6-dirnethoxybenzofuran by electronic impact on 6,7-dimethoxycoumarin. - The Koelsch reaction is kindred it converts coumarine into 2,3-dihydrobenzofuran derivatives. ... 

In a simplistic way, phenolics can be classified according to the number of constitutive carbon atoms in the basic skeleton. With a basic skeleton of Cg, there are simple phenols and benzoquinones with Cg-Ci, there are hydroxybenzoic acids such as gallic acid with Cg-C2, there are the phenylacetic acids and with Cg-Cs, there is a larger class including hydroxycinnamic acids, coumarines, and chromones. Sometimes, these structures... 

Besides compounds 110 and 111, two new compounds (119, 120) representing a novel carbon skeleton having a new stilbene-coumarin nucleus, were isolated from the root bark of Ekebergia benguelensis. The structure of 119 was elucidated by 2D spectral methods and confirmed by single X-ray analysis [65]. 

Phenolics and their functional derivatives are widely found throughout the plant kingdom. One defining characteristic of these compounds is that their aromatic ring usually contains at least one hydroxyl substituent. In a broad sense, phenolics, which are classified according to their structural skeleton, are basically derivatives from simple phenols and phenolic acids, phenylpropanoids including coumarins and lignans, flavonoids and related compounds, and stilbenes. Some of these compounds which show anti-inflammatory activity are reviewed in this section. 

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