Furan 2.3- dihydro-3-carboxylic acid

Furan-2-carboxylic acid, 2,5-dihydro-, ethyl ester H NMR, 4, 573 <75JA5I60)... 

Benzo[6]furan-2-carboxylic acid, 5-acyl-2,3-dihydro-applications, 4, 708... 

Furan-2-carboxylic acid, 3,4,5-triphenyl-dimethyl ester, 4, 691 Furan-3-carboxylic acid, 2,3-dihydro-esters... 

Anodic oxidation of fiirans in acetic acid leads to the 2,5-diacetoxy-2,5-dihydro-furan 58 [185, 186]which is readily converted to 2-acetoxyfiiran, This has proved a valuable intermediate for the synthesis of butenolides [187]. Reactions in moist acetonitrile yield the 2,5-dihydro-2,5-dihydroxyfurans which can be oxidised to the maleic anhydride 59 [188], Oxidation of furan-2-carboxylic acid in methanol and sulphuric acid is a route to the ester of a-ketoglutaric acid [189]. 

Pyrrole polymerises under reducing conditions, Tliiophene-2-carboxylic acid is reduced in alkaline solution at -2.3 V v v. see, on a mercury cathode, to the 2,5-dihydro compoimd [61], Under these same conditions, furan-2-carboxylic acid is also reduced to the 2,5-dihydro compound [62]. 

The last inhibitor from rose seeds was identified as 2,5-dihydro-furan-2-carboxylic acid (2 ). The specific activity of this compound is not very high, but rose seeds contain enough of it to exert measurable inhibition of seed germination. The bioactivity seems to depend on this particular structure because a number of similar compounds (29 - 37) have no activity or much lower activity than 2 . 

It has been demonstrated that the 4,5-dihydro-2-methylfuran, formed as an intermediate, hydrolyzes to 5-hydroxy-2-pentanone through the reaction sequence shown in Scheme 12.25.189,190,192 On the other hand, 5-hydroxy-2-pentanone was cyclodehy-drated to give 4,5-dihydro-2-methylfuran in yields of 86% or more in a continuous process in the presence of phosphoric acid (Scheme 12.25). Furan-2-carboxylic acid (2-furoic acid) was hydrogenated to the corresponding tetrahydro derivative in water over Skita s colloidal palladium at room temperature193 or over Raney Ni in ammo-niacal water at 130-150°C and 0.93 MPa H2 (eq. 12.99)194 or as its sodium salt in water at 110°C and 5.2 MPa H2.195... 

Phenylbenzo[c ]furan-3-carbonitrile and the corresponding carboxylic acid are catalyti-cally reduced in a cis manner to the expected 1,3-dihydro compounds. 1,3-Diaryl-benzo[c]furans are also reduced to phthalans with sodium amalgam. 

Raney nickel reduction of 2-benzyl-5-ethylselenophene (71) yields 1-phenylheptane (72), a conversion analogous to the much used reductive desulfurization of thiophenes (73JGU871). The electrochemical reduction of selenophene-2-carboxylic acid gives a mixture of dimeric products the major product is compound (73). This is in contrast to the 2,5-dihydro derivatives obtained by electrochemical reduction of thiophene and furan carboxylic acids (82CS( 19)95). Wolff-Kishner reduction of 2-selenienyl 2 -thienyl ketone gives, in addition to the expected methylene derivative, 2-(pentenyl)thiophene (72ZOB1780). 

Fig. 16. Chemical structures for Ras inhibitors, (a) GTP analogs with modified bases bind to Ras with up to a Kiel (IC50 of Analog divided by the IC50 of GDP) of 3.30. (b) Sulindac sulfide ((3Z)-3-(4-(methylthio)benzylidene)-6-fluoro-3,3a-dihydro-2-methyl-2H-indene-1 -carboxylic acid) disrupts this interaction with an IC50 of approximately 210 pM. (c) An optimized sulindac analog ((3Z)-6-fluoro-3-((furan-3-yl)methylene)-3,3a-dihydro-2-methyl-2H-indene-1 -carboxylic acid) has an IC50 of approximately 30 pM. The molecular basis of the compound s mechanism of action is unknown, but both (b) and (c) are hypothesized to operate by disrupting Ras-Raf interactions.

Efforts have been focused on the synthesis of 5-ethyl-5,8-dihydro-8-oxofuro[3,2-Z)][l,8]naph-thyridine 7-carboxylic acid (37), known as DJ-6783, due to its wide spectrum of potent antimicrobial activity <86MI 837-01 >. A few synthetic routes have been studied, which were all based on the strategy of constructing the furan ring from naphthyridine derivatives. A synthetic route demonstrated in... 

During the course of the preparation of 8-ethyl-5,8-dihydro-5-oxofuro[2,3-6][l,8]naphthyridine-6-carboxylic acid (108) which is an isomer of (37), the furan ring was constructed by reacting (106) with ethyl bromomalonate (Scheme 9) <80CPB76i>. 

Dihydro-6-hydroxy-2-[5-hydroxy-4-carboxynaphtho[l,2-6]furan-2-yl]-2-methyl-2//-naphtho[l, 2-6]pyran-5-carboxylic acid, D-20061... 

An aq. soln. of KOH added in one portion at room temp, to a suspension of 2,5-dihydro-2-oxo-N-phenyl-4-[(N-phenyl-N-methyl)amino]-3-furancarboxamide in ethanol, and heated under reflux for 2 h 4,5-dihydro-4-oxo-2-phenylamino-3-furan-carboxylic acid. Y 77%. Reverse reaction s. Synth. Meth. 42, 348. F.e.s. R.A. Mack et al., Helv. Chim. Acta 71, 783-7 (1988). 

Benzyl-4,4,6-trimethyl-5,6-dihydro-4H-1,3-oxazine dissolved in tetrahydro-furan-ethanol (1 1), 9 N HGl added to pH 7, then aq. NaBH4 added at -30° with simultaneous addition of more HGl to keep the pH at 7, and stirred 1 hr. at -30° after the addition 2-benzyl-4,4,6-trimethyltetrahydro-l,3-oxazine. Y 88%. - Via this reduction, aldehydes, inch deuterioaldehydes, can be prepared from carboxylic acids and nitriles. F. e. s. A. I. Meyers and A. Nabeya, Ghem. Gommun. 1967, 1163. 

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