Dihydro-4-hydroxy-2 -2//-1 -benzopyran,

V-plieny l- V-ni et hy 1-2-hydroxy-mt-d iaini i iu ro pane (CHlHlfiN20 63062-22-6) see Metaclaz.cpam mM>-[[(phenylmethyl)imino]bis(methylcne) bis[6-fluoro-3,4-dihydro-2AM-benzopyran-2-methanol) stereoisomer (C2 H7 F2N04 129050-28-8) see Nebivolol... 

The 2-phenyl analogue of this compound, 6-acetyl-7,8-di hydroxy-2-phenyl-3,4-dihydro-2H-benzopyran has been prepared in 35% yield by the gradual addition over 6 hours of cinnamyl alcohol in benzene solution to a stirred suspension at 60°C of 2,3,4-trihydroxyacetophenone in orthophosphoric acid in benzene (2 5) with continuance of reaction for a further 12 hours. Some uncyclised material, 5-cinnamyl-2,3,4-trihydroxyacetophenone (25%) was cyclised by heating with phosphoric acid at 80°C at which temperature the starting material furnished only the cyclised product directly in 55% yield (ref. 14). 

Chemicel Neme 2-[2,3-Dihydro-3-(4-hydroxy-3-methoxyphenyll-2-(hydroxymethyll-1,4-benzodioxin-6-yl] -2,3-dihydro-3,5,7-trihydroxy-4H-1 -benzopyran-4-one... 

CN 3,4-dihydro-8-[2-hydroxy-3-[( 1 -methylethyl)amino]propoxy]-2f/-1 -benzopyran-3-ol 3-nitrate... 

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

Chantrapromma, K. et al., 5-Hydroxy-7-methoxy-2-phenyl-4H-l-benzopyran-4-one (tectochrysin) and 2,5-dihydroxy-7-methoxy-2-phenyl-2,3-dihydro-4H-l-benzopyran-4-one isolation from Uvaria rufas and X-ray structures, Aust. J. Chem., 42, 2289, 1989. 

Dihydro-5 -hydroxyamentoflavone 3.4- Dihydro-8-hydroxy-3,5-dimethyl-lH-2-benzopyran-l-one (-)-2,5-Dihydro-5-hydroxy-4-(4 -hydroxyphenyl]-furan- 2-one Methylmellein Hydroxybutenolide... 

Other furocoumarins, although they have rather different structures, have very similar names, which gives rise to confusion. Thus, whereas oroselone (8) is 8-isopropenyl-2//-furo[2,3-A][l]benzopyran-2-one12 and oroselol (9) is 8-(l-hydroxy-l-methylethyl)-2 -furo[2,3- ][l]benzopy-ran-2-one, oreoselone (10) is 2-isopropyl-2,3-dihydro-7 -furo[3,2-gr][l]-benzopyran- 3,7- 2 -dione.13... 

A solution of 80 g (0.34 mol) of ethyl 7-hydroxy-4-oxo-4H-l-benzopyran-2-carboxylate in 60 mL of AcOH and 275 mL of THF was hydrogenated over 4.0 g of 10% Pd on charcoal at 45°C and 65 psi. After hydrogen absorption ceased, the catalyst was removed by filtration and the solvents were evaporated under reduced pressure. Crystallization from CCI4 gave 65 g (85%) of ethyl (R,S)-3,4-dihydro-7-hydroxy-2H-l-benzopyran-2-carboxylate m.p. 80-82°C. 

A stirred mixture of 65 g (0.293 mol) of ethyl (R,S)-3,4-dihydro-7-hydroxy-2H-l-benzopyran-2-carboxylate in 650 mL of AcOH, 1.5 mL of acetic anhydride, and 65 mL of BF3-OEt2 was heated at reflux for 18 h and evaporated. To the residue was added 700 mL of water, and the mixture was stirred at room temperature for 1.0 h. The product was collected by filtration... 

AIL, 3-necked, round-bottomed flask equipped with a mechanical stirrer and an Ar bubbler was charged with 37.5 g (0.179 moles) of 5-bromo-l-pentanyl acetate, 350 mL of anhyd. DMSO, 40.7 g (0.163 mol) of ethyl (R,S)-3,4-dihydro-7-hydroxy-2H-l-benzopyran-2-carboxylate, and 51.0 g (0.369 mol) of powdered potassium carbonate. The mixture was stirred at room temperature for 18 h, poured into 1.0 L of water and extracted into EtOAc (2 1 L). The extract was washed with 1 L of brine, dried and evaporated. The residue was dissolved in 200 mL of ether, cooled to 57°C and, with stirring, diluted with petroleum ether. The product was collected by filtration, washed with a little 1 1 ether-petroleum ether (b.p. 40-60°C) and dried to give 60.0 g (97%) of methyl (R,S)-6-acetyl-3,4-dihydro-7-((5-acetoxypentyl)oxy-2H-l-benzopyran-2-carboxylate m.p.51-53°C. 

A solution of 72.08 g (0.19 mol) of 5-bromo-l-pentanyl acetate in 1.4 L of MeOH was treated with 38 mL of a 1.0 molar solution of tetrabutylammonium hydroxide and the mixture was stirred at room temperature for 3.0 h, 3.0 mL of AcOH was added and the solution was evaporated at 35°C. The residue was dissolved in 400 mL of EtOAc and the solution was washed with saturated NaHC03, brine, dried, and evaporated to give 60.45 g (94% yield) of the intermediate hydroxy ester (an analytical sample may be obtained by crystallization from 70% EtOAc in hexane, m.p. 58-61°C. A stirred solution of 60.25 g of the hydroxyester in 700 mL of EtOAc was cooled to 5°C and treated with 75.5 mL (3 equiv.) of triethylamine and 32.6 mL (2.35 equiv.) of methanesulfonyl chloride. The mixture was stirred at 6°C for 2.0 h, transferred to a separatory funnel and washed sequentially with water, 2 N HCI, and brine. Concentration of the EtOAc to ca. 300 mL and dilution cooled to 0°C and treated with 75.5 mL (3 equiv.) of triethylamine and 32.6 mL (2.35 equiv.) of methanesulfonyl chloride. The mixture was stirred at 6°C for 2.0 h transferred to a separatory funnel and washed sequentially with water, 2 N HCI, and brine. Concentration of the EtOAc to ca. 300 mL and dilution with 250 mL of hexane led to crystallization (0°C, 18 h). The product was collected by filtration and washed with some cold hexane - EtOAc (1 1) to give 66 g (84% yield) of methyl (R,S)-6-acetyl-3,4-dihydro-7-[5-[(methylsufonyl)oxy]pentyloxy]-2H-l-benzopyran-2-carboxylate m.p. 73-76°C. 

A mixture of 66.13 g (0.159 mol) of methyl (R,S)-6-acetyl-3,4-dihydro-7-[5-[(methylsufonyl)oxy]pentyloxy]-2H-l-benzopyran-2-carboxylate, 30.99 g (0.159 mol) of l-[2,4-dihydroxy-3-propylphenyl)ethanone, 33.07 g (0.239 mol) of pulverized potassium carbonate, 5.16 g (15.9 mmol) of tris(3,6-dioxahepyl)amine in 900 mL of toluene was stirred under Ar at reflux for 6 h and then at room temperature overnight. The mixture was poured into 300 mL of water and the organic phase was separated, washed with brine, dried and evaporated to give 84.3 g of methyl (R,S)-6-acetyl-7-[5-(4-acetyl-3-hydroxy-2-propylphenoxy)pentoxy]-3,4-dihydro-2H-l-benzopyran-2-carboxilate. Crystallization from MeOH (0°C, 18 h) gave 66 g (81% yield), m.p. 77-80°C. 

A stirred solution of 55.82 g (0.109 mol) of methyl (R,S)-6-acetyl-7-[5-(4-acetyl-3-hydroxy-2-propylphenoxy)pentoxy]-3,4-dihydro-2H-l-benzopyran-2-carboxylate in 725 mL of MeOH was treated with 4.45 g (0.111 mol) of NaOH in 20 mL of water and the mixture was stirred at reflux for 1.25 h. It was cooled, concentrated to a volume of ca 360 mL, diluted with 310 mL of ether and left at 0°C overnight. The product was collected by filtration, dried in to give 45.76 g of (R,S)-6-acetyl-7-[[5-(4-acetyl-3-hydroxy-2-propylphenoxy)pentyl]oxy]-3,4-dihydro-2H-H-benzopyran-2-carboxylic acid sodium salt (Ablukast) as the monohydrate. A further 12.27 g of product was obtained from the mother liquor to give a total yield of 99%. 

One of six chromenone glycosides isolated from the tubers of Eranthis hyemalis and structurally identified by a combination of FAB-MS and 2D (COSY, COLOC) NMR techniques was compound (15), a / -D-glucopyranoside of 7-(hydroxymethyl)-2,3-dihydro-2-(l-hydroxy-l-methylethyl)-4-methoxy-5/7-furo[3,2- ][l]benzopyran-5-one <91HCA611). 

SYNS (R)N-((5-CHLORO-3,4-DIHYDRO-8-HYDROXY-3-METH L-l-OXO-lH-2-BENZOPYRAN-7-YL))PHENYL-ALANINE NCI-C56586 D OCHRATOXIN A... 

A useful extension of the alkoxycarbonylation reaction has been devised in order to obtain 3,4-dihydro-4-hydroxy-l//-2-benzopyran-3-acetic acid lactones from 5-alkene-l,4-diols. The intramolecular cyclization of 7, carried out with palladium(II) acetate and copper(II) chloride under a carbon monoxide atmosphere, affords the m-lactone 8 in 68% yield. The configuration is assigned on the basis of H-NMR double resonance methods86. 

Synonyms (2S)-7-[[6-0-(6-Deoxy-a-L-mannopyranosyl)-P-D-glucopyranosyl]oxy]-2,3-dihydro-5-hydroxy-2-(3-hydroxy-4-methoxyphenyl)-4H-l-benzopyran-4-one hesperitin 7-rhamnoglucoside hesperetin-7-rutinoside. 

Figure 8.1. Structure of (K)-A -[(5-chloro-3,4-dihydro-8-hydroxy-3-methyl-l-oxo-ll/-2-benzopyran-7-yl)carbonyl]-L-phenylalanine) (OTA).

Hydroxy-l-oxo-2-methoxycarbonyl-2,3-dihydro-inden (F 131-132°) und l-Hydroxy-3-mdhoxy-carbonyl-III-(2-benzopyran y (F 110 1110)1 ... 

Athamantin. 3-Methyibutanoic acid 8,9-dihydro-8-fl-m ethyl-I-(3-me thy i-I -oxobutoxy)ethylJ-2-oxo-2H-furo[2,3-h]-l. benzopyran-9-yl ester isovaleric acid diester with 8,9-dihydro-9-hydroxy-8-(l-hydroxy-l-methyUihyl)-... 

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