L//- Benzopyrans

The alkaloid reserpiae [50-55-5] which is isolated from the roots of Kauwoljia serpentina T., contains a gaUate trimethyl ether moiety. Reserpiae is used as an antihypertensive and a tranquilizer. A vinylogue of reserpiae, rescinnamine [24815-24-5] is also an antihypersensitive (75). Methoxsalen [298-81-7] (8-methoxypsoralen 7JT-9-methoxy-furo [3,2- ] [l]benzopyran-7-one) (21), a furocoumatia that occurs ia plants, eg, l eguminosae and Umbelliferae is used ia the treatment of vitiligo, as a suntanning promoter, and as a sunburn protectant. It is also available by synthesis (76). 

R = C6H5 methyl 4-ben oylamino-6-fluoro-3,4-dihydro-2-methyl-2 -l-benzopyran-4-carhoxylate yield 85% d.r. (trans/cis) 72 28... 

CN [[3-[2-(diethylamino)ethyl]-4-methyl-2-oxo-2//-l-benzopyran-7-yl]oxy]acetic acid ethyl ester... 

CN 5-[[4-(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2//-l-benzopyran-2-yl)methoxy]pheny ]methyl-2,4-thiazolidinedione... 

Several aryl esters of 6-chloromethyl-2-oxo-2//-l -benzopyran-3-carboxylic acid act as human Lon protease inhibitors (alternate substrate inhibitors)46 without having any effect on the 20S proteasome. Proteasomes are the major agents of protein turnover and the breakdown of oxidized proteins in the cytosol and nucleus of eukaryotic cells,47 whereas Lon protease seems to play a major role in the elimination of oxidatively modified proteins in the mitochondrial matrix. The coumarin derivatives are potentially useful tools for investigating the various biological roles of Lon protease without interfering with the proteasome inhibition. 

New rearrangements of 2-imino-2//-l-benzopyran-3-carboxamides under the action of anthranilic acid as an N-nucleophile have been revealed. Depending on the conditions 2-(2-oxo-2//-l-benzopyran-2-yl)-3//-quinazolin-4-ones or 2-oxo-2//-l-benzo-pyran-3-((V-2-carboxyphenyl)carboxamides were found to be the products. 

Methylbenzimidazole, see 2-Nitroaniline Methyl 2-benzimidazole carbamate, see Benomvl Methyl benzoate, see Sulfometuron-methvl 4-Methyl-2//-l-benzopyran-2-one, see Naphthalene o-Methylbenzoquinone, see Aminocarb p-Methylbenzoquinone, see Toluene... 

Keywords Acetals, Acylals, Allylations, Bismuth(III), 3,4-Dihydro-2//-l -benzopyrans, Ene reactions, Epoxide-olefin cyclizations, Piperidines, Tetrahydro-quinolines, THP ethers... 

Scheme 3 Bismuth(III) triflate-catalyzed synthesis of substituted 3,4-dihydro-2//-l-benzopyrans...

Baumy et al. (27) determined the binding constants for two 3,4-dihydro-2//-l-benzopyran derivatives of /3-CD. These binding constants were then used to calculate the optimal concentration of chiral selector for the enantioseparation of the two compounds. The calculation of the optimal concentration of the chiral selector was performed according to Eq. (18). Good agreement was found between the calculated and experimentally observed optimum concentrations for the two compounds. 

Similarly, reaction of 2-dimethylaminomethylene-3-oxoalkanoates or 2-di-methylaminomethylene-1,3-cyclohexanediones with 2-phenyl-5(4/7)-oxazolone 146, generated in situ from hippuric acid, affords 6-substituted 3-(benzoyl-amino)-2-oxo-2//-pyran-5-carboxylates 204 and 3-(benzoylamino)-7,8-dihydro-2//-l-benzopyran-2,5(6//)-diones 206, respectively. These compounds showed strong local anesthetic activity (Scheme 7.62). ... 

A series of 3-alkyl- and 3-aryl-7/7-furo[3,2- ]-l-benzopyran-7-ones 78 (linear furocoumarins) was synthesized and evaluated for their photochemical and nonphotochemical crosslink formation with DNA as well as for their spectro-photometric and fluorescent properties, lipophilicity, and ability to photobleach A, A -dimethyl-/)-nitrosoaniline (RNO) after irradiation with UVA light <2002AP187>. The synthesis of the linear furocoumarins (Scheme 10) was a modification of a previously published method in which 7-hydroxy-2//-l-benzopyran-2-ones 76 were converted into / -ketoethers 77 by alkylation with haloketones under phase-transfer catalysis conditions. Base-catalyzed intramolecular condensation and subsequent acidification gave the corresponding 78. A molecular complex between each one of these fluorescent furocoumarins and DNA was observed, but only compounds with a 3-Me or 3-Ph group showed UVA irradiation-induced crosslink formation. 

Chem. Abstr. Serv. Reg. No. 91-64-5 Chem. Abstr. Name 2//-l-Benzopyran-2-one lUPAC Systematic Name Coumarin... 

Spiro tetrahydroquinoxaline-2,2 -[l]benzopyran (247) has been obtained from l,2,4-trimethyl-3-oxo-3,4-dihydroquinoxalinium metho-sulfate with salicylaldehyde.239... 

The pyrolysis of ( )-3-(pentafluorophenyl)prop-2-enoic acid at 400 C in vacuo yields 5,6,7,8-tetrafluoro-2//-l-benzopyran-2-one (4).135... 

The action of sodium methoxide or potassium hydroxide on 2,3,3,3-tetrafluoro-1-(2-hydroxy-phenyl)propan-l-one gives 3-fluoro-4-hydroxy-2//-l-benzopyran-2-one (8).137... 

Analogously, 6//-[l]benzopyrano[4,3-6][l, 5]benzothiazepin-6-one (151) was obtained by a cyclocondensation reaction using 3-formyl-2//-l-benzopyran-2-one (150) and 5 (Scheme 47) (91M77). 

Bcnzo[/)]furan and derivatives, recent advances in chemistry of, Part 1, occurrence and synthesis, 18, 337 Benzo[c]furans, 26, 135 recent advances in the chemistry of, and related compounds, 73, 1 Benzofuroxans, 10, 1 29, 251 2//-l-Benzopyrans (chrom-3-enes), 18, 159 Bcnzofc] pyrylium salts syntheses, reactions, and physical properties, 50, 157 1,2-and 2,1-Benzothiazines and related compounds, 28, 73... 

Kiehlmann E., Conn J. E. and Borden J. H. (1982) 7-Ethoxy-6-methoxy-2,2-dimethyl-2//-l-benzopyran. Org. Prep. Proc. Int. 14, 337. 

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