Furan-2 -ones, 5-hydroxy

In elucidating the structure of nupharamine Arata and Ohashi (35) resorted to systematic degradation, of which the more important steps are shown in Chart II. Their analytic data have shown the alkaloid to be a secondary amine incorporating one hydroxy and two methyl groups IR-spectra indicate the presence of a furan ring (35). 

Benzo[c]furan-4,7-dione, l-(2-hydroxy-6-methoxyphenyl)-5-methyl-X-ray, 4, 540 <80JCS(P1)2447> Benzo[c]furan-l(3H)-one, 5-methyl-4,7-dimethoxy-... 

H-Benzo[a]carbazole, 4,4a,5,l 1,1 la,l Ib-hexahydro-synthesis, 4, 283 Benzo[b]carbazole, N-acetyl-photochemical rearrangements, 4, 204 Benzo[/]chroman-4-one, 9-hydroxy-2,2-dimethyl-synthesis, 3, 851 Benzochromanones synthesis, 3, 850, 851, 855 Benzochromones synthesis, 3, 821 Benzocinnoline-N-imide ring expansion, 7, 255 Benzocinnolines synthesis, 2, 69, 75 UV, 2, 127 Benzocoumarins synthesis, 3, 810 Benzo[15]crown-5 potassium complex crystal stmcture, 7, 735 sodium complex crystal stmcture, 7, 735 Benzo[ 18]cr own-6 membrane transport and, 7, 756 Benzo[b]cyclohepta[d]furans synthesis, 4, 106 Benzocycloheptathi azoles synthesis, 5, 120... 

A tautomeric equilibrium of 4-hydroxy-benzo[c]furan-3(l//)-ones of type 199 has been reported [R, R = Me, (CH2)4, (CH2)5] (89KGS24). 

C7H14O 111-71-7) see Undecylenic acid [3a/ -(3aa,4a,SP,6aa)]-4-[2-(2-heptyl-l,3-dioxolan-2-yl)ethyl]hexahydro-5-hydroxy-2//-cyclopenta[6]furan-2-one... 

A stmple and general synthesis of 2,2,4,5-tetrasubstituted furan-3(2//)-ones from 4-hydroxyalk-2-ynones and alkyl halides via tandem CO, addition-elimination protocol is described <96S 1431>. Palladiuni-mediated intramolecular cyclization of substituted pentynoic adds offers a new route to y-arylidenebutyrolactones <96TL1429>. The first total synthesis of (-)-goniofupyrone 39 was reported. Constmction of the dioxabicyclo[4.3.0]nonenone skeleton was achieved by tosylation of an allylic hydroxy group, followed by exposure to TBAF-HF <96TL5389>. 

XVII XVII, 1st Supplement 1933 2359-2503 One Cyclic Oxygen (S, Se or Te). Stem nuclei Furan, 27. Thiophene, 29. Hydroxy compounds Furfuryl alcohol. 

This gives tautomeric mixtures119 when the tert-butyl group is removed. The methyl ether has been used to obtain 3-hydroxy-2-carbonyl derivatives in the selenophene series.120 The unsubstituted 2-hydroxyselenophene system has been prepared by hydrogen peroxide oxidation of 2-selenophene-boronic acid.121 However, in the 5-methyl-substituted system deboronation became such an important side reaction that 5-methyl-2-hydroxyselenophene had to be prepared by acid-catalyzed dealkylation of 5-methyl-2-fert-butoxy-selenophene. Both 2-hydroxy- and 5-methyl-2-hydroxyselenophene exist mainly as 3-selenolene-2-ones (93) and for the 5-methyl derivative it was possible to isolate the / ,y-unsaturated form (92) and follow the tautomeric isomerization. The activation parameters thus obtained were compared with those for the corresponding furan and thiophene systems. 

In contrast to the rich chemistry of alkoxy- and aryloxyallenes, synthetic applications of nitrogen-substituted allenes are much less developed. Lithiation at the C-l position followed by addition of electrophiles can also be applied to nitrogen-containing allenes [10]. Some representative examples with dimethyl sulfide and carbonyl compounds are depicted in Scheme 8.73 [147, 157]. a-Hydroxy-substituted (benzotriazo-le) allenes 272 are accessible in a one-pot procedure described by Katritzky and Verin, who generated allenyl anion 271 and trapped it with carbonyl compounds to furnish products 272 [147]. The subsequent cyclization of 272 leading to dihydro-furan derivative 273 was achieved under similar conditions to those already mentioned for oxygen-substituted allenes. 

PHOTOINDUCED-ADDITION OF METHANOL TO (5S)-(5-0-tert-BUTYL-DIMETHYLSILOXYMETHYL)FURAN-2(5H)-ONE (4R,5S)-4-HYDROXY-METHYL-(5-0-tert-BUTYLDIMETHYL-SILOXYMETHYL)FURAN-2(5H)-ONE... 

The photoinduced-addition of alcohols to cycloalkenones has been investigated by Fraser-Reid and co-workers,4 by Paquette,5 and was used as the key step in the synthesis of the prostaglandin endoperoxide analogue (15S)-hydroxy-9a,11a-epoxymethanoprosta-(52,13E)-dienoic acid,6 and for the recent synthesis of 2, 3 -dideoxy-3 -hydroxymethyl-5 -carbanucleosides.7 No work (other than our own) has been reported on the photoinduced-addition of alcohols to 5-substituted furan-2(5H)-ones. 

Thermolysis of D-fructose in acid solution provides 11 and 2-(2-hydrox-yacetyl)furan (44) as major products. Earlier work had established the presence of 44 in the product mixtures obtained after acid-catalyzed dehydrations of D-glucose and sucrose. Eleven other products were identified in the D-fructose reaction-mixture, including formic acid, acetic acid, 2-furaldehyde, levulinic acid, 2-acetyl-3-hydroxyfuran (isomaltol), and 4-hydroxy-2-(hydroxymethyl)-5-methyl-3(2//)-furanone (59). Acetic acid and formic acid can be formed by an acid-catalyzed decomposition of 2-acetyl-3-hydroxyfuran, whereas levulinic acid is a degradation prod-uct of 11. 2,3-Dihydro-3,5-dihydroxy-6-methyl-4//-pyran-4-one has also been isolated after acid treatment of D-fructose.The pyranone is a dehydration product of the pyranose form of l-deoxy-D-eo f o-2,3-hexodiulose. In aqueous acid seems to be the major reaction product of the pyranone. 

Hydroxy-2-methyl-4//-pyran-4-one (maltol) and 2-acetyl-3-hydroxy-furan (isomaltol) are also products of the Maillard reaction. Both have a considerable history, due to their early detection in beer and breads. A mechanism based upon the pyranose form of a methyl-a-dicarbonyl inter-... 

In regard to the importance of a diastereoselective synthesis of 5-[hydroxy(aryl) methyl]furan-2(5//)-ones, the Bi(OTf)3-4H20-catalyzed vinylogous Mukaiyama aldol has been investigated with 2-(trimethylsilyloxy)furans and various carbonyl compounds [146]. 

Among the various polar solvents tested, acetonitrile, dichloromethane, and THF afforded good yields of the expected product, although with moderate diastereo-selectivity (Table 16, entries 1-3). The most suitable solvent was found to be diethyl ether. 5-[Hydroxy(phenyl)methyl furan-2(5//)-one 28a was obtained with the best yield and diastereoselectivity (Table 16, entry 4). With further optimization of the reaction conditions, we found that a lower catalyst loading (0.5 mol%) did not allow the reaction to proceed (Table 16, compare entries 5 and 4), although a higher catalyst loading (5 mol%) afforded the product with close diastereoselectivity but decreased yield (Table 16, compare entries 6 and 4). 

Furan-3-one, tetrahydro, 2-methyl LP Furocoumarin, angular, 4-hydroxy-2 -methoxy LP ... 

Amino acid-modified furocoumarins were prepared by condensation of the T-hydroxysuccinimide ester of 3-(2,3,5-trimethyl-7-oxofuro[3,2-g]chromen-6-yl)propanoic acid 51 with amino acids <2003JPH177>. Ethyl 3-(7-hydroxy-4-methyl-2-oxo-2/7-3-chromenyl)propanoate 49, prepared in 56% yield by Pechmann condensation of resorcinol and diethyl 2-acetylglutarate in the presence of HCl, was condensed with 3-chlorobutan-2-one in the presence of base to give propanoate 50 (Scheme 4). The MacLeod method was then used to fuse a furan ring to the benzopyran-2-one system. Heating 50 with NaOH solution (1 M) readily cyclized it into the corresponding psoralen furocoumarin 51 with simultaneous hydrolysis of the ester. 

Numerous furan and pyran derivatives, many of which originate from heat treatment of carbohydrates, largely determine the odor of processed foods. Of this group, 2,5-dimethyl-4-hydroxy-277-furan-3-one and maltols are used in fairly large quantities in flavors. The following compounds are used in relatively small amounts in flavor compositions ... 

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