5.7- Dimethoxy-8- -coumarin

The synthesis of 5,7-dimethoxy coumarin 39 started from phloroglucinol through coumarin construction by Pechman reaction followed by methylation via two steps. The resulting 8-tigloylated coumarin 40 (Scheme 8-9) was obtained by treatment of the coumarin (39) with tigloyl chloride according to the preparation method described in Scheme 8-8. 

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]. 

Coumarin and some of its methoxy-derivatives undergo acetoxymethylation, usually at C-3, in yields of up to 87% when heated with manganese(iii) acetate in a solvent such as acetic acid-acetic anhydride. Varying amounts of the 3-(diacetoxymethyl)-derivatives were also isolated in some experiments, and in the reaction with 7,8-dimethoxycoumarin the benzene ring was sufficiently reactive to allow the formation of 3,6-di(acetoxymethyl)-7,8-dimethoxy-coumarin. Ring-contraction of 4-(chloromethyl)coumarin in aqueous alkali proceeded in 92% yield to give benzofuran-3-acetic acid. " ... 

Coumarin, 3,4-dihydro-4-phenyl-synthesis, 3, 848 Coumarin, 6,7-dihydroxy-molecular structure, 3, 622 Coumarin, 7,8-dihydroxy-molecular structure, 3, 622 Coumarin, 6,7-dimethoxy-mass spectra, 3, 610... 

Intermediates generated at an electrode surface may react while still near the electrode. If so, one side of the intermediate may be wholly or partly shielded from attack by other reactants by the electrode itself. Such behavior is particularly common in the electrochemical oxidation of aromatic compounds since, as we have already seen with coumarin, aromatic compounds are generally tightly adsorbed parallel to the electrode surface at potentials positive of the p.z.c. For example, electrochemical oxidation of the stilbenes in alkaline methanol affords a mixture of dl and meso-1,2 dimethoxy-1,2-diphenylethane (1) 10>. It is found that c/s-stilbene affords a mixture of isomers of 1 in which the... 

Kwakman et al. [65] described the synthesis of a new dansyl derivative for carboxylic acids. The label, N- (bromoacetyl)-A -[5-(dimethylamino)naphthalene-l-sulfonyl]-piperazine, reacted with both aliphatic and aromatic carboxylic acids in less than 30 min. Excess reagent was converted to a relatively polar compound and subsequently separated from the derivatives on a silica cartridge. A separation of carboxylic acid enantiomers was performed after labeling with either of three chiral labels and the applicability of the method was demonstrated by determinations of racemic ibuprofen in rat plasma and human urine [66], Other examples of labels used to derivatize carboxylic acids are 3-aminoperylene [67], various coumarin compounds [68], 9-anthracenemethanol [69], 6,7-dimethoxy-l-methyl-2(lH)-quinoxalinone-3-propionylcarboxylic acid hydrazide (quinoxalinone) [70], and a quinolizinocoumarin derivative termed Lumarin 4 [71],... 

About seven commonly occurring coumarins were found in A. annua, namely scopoletin, scopolin, aesculetin, 6,8-dimethoxy-7-hydroxy coumarin, 5,6-dimethoxy-7-hydroxy coumarin, tomentin, and coumarin. " ... 

A cyclization of a dimethoxy cinnamic acid to a coumarin derivative is presented by... 

Condensation of 4,6-dimethoxy-2-hydroxyacetophenone with diethyl carbonate and an alkoxide ion has now been shown to give the coumarin-3-carboxylic ester (245), and not 4-hydroxy-5,7-dimethoxycoumarin (246), as originally reported. Heating the ester with aqueous alkali resulted in hydrolysis and decarboxylation to (246). The well-established acid cyclization of salicyl-aldehyde with ethyl cyanoacetate to give coumarin-3-carboxylic acids has been studied in alkaline media and found to give the ester (247 X = O) and the imino-ester (247 X = NH). When the proportion of the cyano-ester was increased, high yields of the latter were obtained. "... 

Two natural antiparasitic coumarins, 5-0-p-D-glucopyranosyl-7,4 -dimethoxy-3 -hydroxy-4-phenylcoumarin and 5-0-P-D-glucopyranosyl-7-methoxy-3, 4 -dihydroxy-4-phenylcoumarin (Fig. 2) isolated from Hintonia latiflora stem bark, have been reported to exhibit antimalarial activity against the development of Plasmodium berghei schizonts in vitro, the second one also showing significant activity in vivo [79]. 

Bhide, B.H., and D.I. Brahmbhatt Isocoumarins Part 4. Synthesis of 5,6-dimeth-oxy-, 6,7-dimethoxy-, 7,8-dimethoxy-, 5,7-dimethoxy-, 5,8-dimethoxy-3-methyliso-coumarins and a New Synthesis of ( )-6-Methoxymellein. Proc. Indian Acad. Sci. 89, 525 (1980). 

In chronic brucellosis, Brucella abortus infects macrophages, thus eluding the immune response [253]. When immunostimulatory drugs such as couma-rin were administered, the symptoms of chronic brucellosis disappeared. These results have encouraged the use of coumarin in other chronic infections such as mononucleosis (Epstein-Barr virus), mycoplasmosis (Mycoplasma pneumoniae), toxoplasmosis (Toxoplasma gondii), and Q fever (Coxiella burnetii). Also, another antiplasmodial coumarin derivate called 5,7-dimethoxy-8-(3 -hydroxy-3 methyl-l -butene)-coumarin has been isolated from the roots of the plant Toddalia asiatica. This finding supports the traditional use of this plant for the treatment of malaria [254]. 

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