Furan acid synthesis

Benzo[c]furan, 1,3,4,7-tetraphenyl-steric hindrance, 4, 542 synthesis, 4, 683 Benzo[b]furan-3-acetic acid synthesis, 3, 686 Benzo[b]furan-3-amine, 2-acyl-tautomerism, 4, 648 Benzo[b]furan-2-carboxamides synthesis, 3, 685... 

Oxoglutarate can also serve as a starter piece for elongation by the oxoacid pathway. Extension by three carbon atoms yields 2-oxosuberate (Eq. 21-1). This dicarboxylate is converted by reactions shown in Eq. 24-39 into biotin and in archaebacteria into the coenzyme 7-mercaptoheptanoylthreonine phosphate (HTP), Eq. 21-1. Lipoic acid is also synthesized from a fatty acid, the eight-carbon octanoate. A fatty acid synthase system that utilizes a mitochondrial ACP may have as its primary fimction the synthesis of ocfanoate for lipoic acid formation. The mechanism of insertion of the two sulfur atoms to form lipoate (Chapter 15) is imcerfain. If requires an iron-sulfur protein jg probably similar to the corresponding process in the synthesis of biotin (Eq. 24-39)9 93a formation of HTP (Eq. 21-1). One component of the archaebacterial cofactor methano-furan (Chapter 15) is a tetracarboxylic acid that is formed from 2-oxoglufarafe by successive condensations with two malonic acid imits as in fatty acid synthesis. ... 

Therapeutics. Compounds containing the furan or tetrahydrofuran ring are biologically active and are present in a number of pharmaceutical products. Eurfurjdamine [617-89-0] is an intermediate in the diuretic, furosemide. Tetrahydrofurfurylamine [4795-29-3] may also have pharmaceutical applications. 5-(E)imethyiaininomethyi)furfuryi alcohol [15433-79-17 is an intermediate in the preparation of ranitidine, which is used for treating ulcers. 2-Acet5dfuran [1192-62-7] prepared from acetic anhydride and furan is an intermediate in the synthesis of cefuroxime, a penicillin derivative. 2-Euroic acid is prepared by the oxidation of furfural. Both furoic acid [88-14-2] and furoyl chloride [527-69-5] are used as pharmaceutical intermediates. 

The acid promoted cyclization of AT-(2-chloroallyl)enaminones (Scheme 35a) provides the expected 3-methyltetrahydroindoles, whereas similar treatment of iV-(2-chloroallyl)anilines yields unexpectedly 2-, rather than 3-, methylindoles (Scheme 35b) (75JCS(Pl)U46). The course of the latter cyclization is not resolved although various intermediates, such as those shown, have been considered. The ring closure in the furan synthesis shown in Scheme 35c is catalyzed by mercury(II) ion (79JCs(Pl)316l). 

C- F coupling constants, 4, 569 Benzo[b]furan-5-carboxylic acid, 4-hydroxy-2-isopropyl-synthesis, 3, 698... 

Furan-2-carbonyl chloride, 5-alkyl-3,4-dichloro-synthesis, 4, 690 Furancarboxamides rotational isomerism, 4, 543 Furan-2-carboxylic acid, 5-acetylamino-ethyl ester reactions, 4, 647 Furan-2-carboxylic acid, amino-properties, 4, 708 Furan-2-carboxylic acid, 5-bromo-nitration, 4, 603, 711 Furan-2-carboxylic acid, 3-methyl-methyl ester bromination, 4, 604 Furan-2-carboxylic acid, 5-methyl-nitration, 4, 602... 

Furan-3-carboxylic acid, 2-methoxy-4-methyl-methyl ester synthesis, 4, 686... 

The final variation of the Feist-Benary furan synthesis encompasses reactions of 1,3-dicarbonyls with 1,2-dibromoethyl acetate (52). For example, treatment of ethyl acetoacetate (9) with sodium hydride followed by addition of 52 at 50°C yields dihydrofuran 53. The product can be easily converted into the corresponding 2-methyl-3-furoate upon acid catalyzed elimination of the acetate, thus providing another strategy for the synthesis of 2,3-disubstituted furans. 

Treatment of 1,4-dicarbonyls (1) with catalytic acid yields substituted furans (2) and is called the Paal-Knorr furan synthesis. This method is used extensively to produce a variety of mono-, di-, tri-, and tetrasubstituted furans. ... 

Ibers used the Paal-Knorr furan synthesis to prepare a key intermediate for the synthesis of novel porphyrin-like aromatic macrocycles. Bis yrolyljfuran 27 was available in good yield via the acid catalyzed condensation of diketone 26. ... 

A biarylpropionic acid derivative containing a furan ring as a prominent feature has antiinflammatory activity. The patented synthesis involves a straightforward organometal1ic addition of ethyl lithioacetate to aldehyde 12 followed by saponification... 

Scheme 3b). It is instructive at this point to reiterate that the furan nucleus can be used in synthesis as a progenitor for a 1,4-dicarbonyl. Whereas the action of aqueous acid on a furan is known to provide direct access to a 1,4-dicarbonyl compound, exposure of a furan to an alcohol and an acid catalyst should result in the formation of a 1,4-diketal. Indeed, when a solution of intermediate 15 in benzene is treated with excess ethylene glycol, a catalytic amount of / ara-toluenesulfonic acid, and a trace of hydroquinone at reflux, bisethylene ketal 14 is formed in a yield of 71 %. The azeotropic removal of water provides a driving force for the ketalization reaction, and the presence of a trace of hydroquinone suppresses the formation of polymeric material. Through a Finkelstein reaction,14 the action of sodium iodide on primary bromide 14 results in the formation of primary iodide 23, a substance which is then treated, in crude form, with triphenylphosphine to give crystalline phosphonium iodide 24 in a yield of 93 % from 14.

Diels-Alder reaction of the furan derivative 148 with homochiral bicyclic enone 149 is the key step [56] in the total synthesis of the diterpenes jatropho-lone A and B, 151 and 152, respectively, isolated from Jatropha gossypiifolia L [57], Initial efforts to carry out the cycloaddition between 148 and 149 under thermal or Lewis-acid conditions failed due to diene instability. Application of 5kbar of pressure to a neat 1 1 mixture of diene and dienophile afforded crystalline 150 with the desired regiochemistry (Scheme 5.23). Subsequent aromatization, introduction of the methylene group, oxidation and methylation afforded (-l-)-jatropholones 151 and 152. 

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