Chromone methyl

Spirothiopyrans 45b including a benzopyrylium ring have been prepared in one step by condensation of 2-aminovinyl-3-formyl chromone-4-thione 47 with 1,2,3,3-tetramethylindolinium salts in ethanol (Scheme 25).90 The precursor 47 is prepared from 3-carboxymethylene-2-methyl-chromone-4-thione 48. First, oxidation of 48 with pyridinium dichromate in CH2C12, and then condensation with dimethyl formamide dimethyl acetal in benzene gave compound 47. 

The formation of such chromones as 3,8-dihydroxy-2-methyl-chromone by treating uronic acids or pentoses with dilute acid was reported by Aso,119 and studied by Popoff and Theander,120 who obtained a number of these compounds in 3.5% yield, as well as some catechols. Although nothing is yet known about the mechanism of formation of these compounds, the fact that the chromones contain 10 carbon atoms and are produced both from pentoses and uronic acids suggests that they may be derived from 2-furaldehyde or re-ductic acid, or produced from a decarboxylated intermediate. 

Simple chromones are less susceptible to photolysis but 3,5,7-trimethoxy-2-methyl-chromone (369) is converted into a dimer which may have structure (370) (73TL5073). The 3-benzylchromone (371) is cyclized to the tetracycline analogue (372) (72JCS(P1)1103). 

PCS-catalyzed condensation of five molecules of malonyl-CoA to produce 5,7-dihydroxy-2-methyl chromone new to this plant (40). Another novel Aloe arborescens type III PKS that produces two hitherto unknown aromatic octaketides, SEK4 and SEK4b, has recently been reported (41). The application of plant cell cultures for the production of the polyketide hypericin from St. John s wort (Hypericum performatum, Hypericaceae) has been investigated (42). 

In the same manner as acetophenones some other methyl compounds can also be transformed with salts (8) to the corresponding phenyl compounds. 2-Methyl-chromone (19), and likewise 2,6-dimethyl-4-pyrone by double conversion, lead to flavone (20) and 2,6-diphenyl-4-pyrone respectively36. Even the very weak acid methyl groups in methylphenylsulphone and in 6-methylazulene (21) may be smoothly transformed. A 100% excess of (<5) and added sodium methoxide in this... 

The natural compound khellin generated two families of cardioactive drugs on one side the benzopyrones, illustrated by the 3-methyl-chromone and chromonar (carbochromen), on the other side the benzofurans, illus-... 

The 4-position of coumarins is the only one at which alkyl snbstitnents have enhanced acidity in their hydrogens, and this is considerably less than that of the methyl gronps of 2-methyl-chromones. ... 

Although chromone-3-carboxaldehyde is readily prepared, the 2-isomer is much less readily available. Selective reduction of methyl chromone-2-carbox-ylate with NaBH4 and MeOH has given the 2-hydroxymethyl compound, apparently without affecting the carbonyl group of the pyrone oxidation with... 

A mixture of methyl chromone-2-carboxylate and SOCI2 refluxed 10 hrs., the resulting crude methyl 4,4-dichlorochromene-2-carboxylate dissolved in benzene, mixed with a soln. of aniline in the same solvent, shaken vigorously, and allowed to stand ca. 16 hrs. methyl 4-(phenylimino)chromene-2-carboxylate. 

Methyl cumarm 17, 337,1174, II363. 5(oder 7) Methyl-chromon 17, 3%. 

Also obtained by hydrolysis of 6-iodo-7-methoxy-2-methyl-chromone by boiling 10% aqueous sodium hydroxide solution [1924],... 

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