Furanoid acid

Furanoid acids/esters such as [6] can be produced from conjugated dienes and from a range of saturated or unsaturated oxygenated acids (hydroxy, epoxy, oxo). These include the following reactions ... 

Acidic dehydration of 1,4-diketo acids, as in the conversion of 9,12-dioxostearic acid to the 9,12-furanoid acid, effected with methanolic BF3 (10). 1,4-Diketones, made from ricinoleate, linoleate, or diynoic esters by Lie Ken lie and his colleagues (22-25), were converted to furanoid acids under acidic conditions (BF3 or toluenesulfonic acid). With 1,4-, 1,5-, and 1,6-diketones, ketocy-clopentenes and ketocyclohexenes were also obtained. Typical products ([7]-[9]) are formulated ... 

Grmstone, F.D., and R.C. Wijesundera, Some Reactions of Long-Chain Oxygenated Acids with Special Reference to Those Furnishing Furanoid Acids, Chem. Phys. Lipids 24 193-208 (1979). 

Branched-chain acids [in addition to phytol-based acids (this section) and furanoid acids (Section 1.10)] have been identified in a number of aquatic sources. These include monoene acids such as 7-methylhexadec-6 and 7-enoic acids and 5-methyl-tetradec-4-enoic add. Some marine animals have a deposit of lipid in the head (melon), an organ which has been implicated in the echo-locating abilities of these animals. These lipids are rich in isovaleric acid (3-methylbutanoic) and iso acids of more conventional chain length but there is no evidence that... 

The most common member of a series of furanoid acids varying in chain length and in the number of methyl groups. Present in fish lipids and reaching high proportions in starved fish. 

It is now shown that the predominant furanoid acid (8) in Hevea... 

The features common to 2-deoxy ribose 5-phosphate and the two 3-deoxy hexulosonic acid 6-phosphates are that they all have a deoxy group next to the carbonyl group and that they can form only the furanoid ring (35, 78a, 80a) as long as the phosphate group is attached to the terminal, primary alcohol. However, they can all assume the pyranoid ring... 

The furanoid vinyl ethers described above are of interest in view of the structure of the nucleoside antibiotic angustmycin A (2) (15) which also contains an exocyclic double bond. As a first step towards the synthesis of analogs of angustmycin A (2), preparation of exocyclic vinyl ethers from hexulofuranoid derivatives was studied. Benzoylation of 2,3 4,6-di-0-isopropylidene-a-L-ryZo-hexulofuranose (44) followed by selective acid hydrolysis of the 4,6-O-isopropylidene group afforded l-0-benzoyl-2,3-0-isopropylidene-a-L-ryZohexulofuranose (45) in 72%... 

Natural products find a place not as such but at points where, once again, their chemistry illustrates the behavior of their furan nuclei. There are now so many naturally occurring furans (the sea adds its quota to the land plant count every week) that even to make a list, as in the previous review, was too big a task and would have taken too much room happily, reference to almost any issue of Phytochemistry will immediately supply examples and there are already some good lists available elsewhere (eremophilane2 and farnesane23 furans, butenolides,3 furanoid fatty acids,4 marine products5). 

Epoxides (oxirans) and 1,2-diols can also be looked upon as disguised ketones capable of being unmasked by acids. Since its development by Spencer et al49 the idea has been utilized by several other groups who used protic acids in work aimed at syntheses of methyl lambertianate,50 a rare furanoid fatty acid from an Exocarpus species,51 and a terpenoid furan,... 

The methyl ester 107 was obtained by treatment of ammonium KDO with methanol in the presence of an acidic catalyst,79 and it is likely that these esterification conditions (rather than the presence of the ester group of itself) favor the furanoid form. It would be of interest to ascertain whether the methyl ester (111) of KDO, when prepared by Zemplen deacetylation of 70 (see Scheme 31), would also yield furanoid derivatives upon benzoylation with benzoyl chloride in pyridine. 

Tipson devoted most of his years in Levene s laboratory accomplishing seminal work on the components of nucleic acids. To determine the ring forms of the ribose component of the ribonucleosides he applied Haworth s methylation technique and established the furanoid structure for the sugar in adenosine, guanosine, uridine, and thymidine. He showed that formation of a monotrityl ether is not a reliable proof for the presence of a primary alcohol group in a nucleoside, whereas a tosyl ester that is readily displaced by iodide affords clear evidence that the ester is at the 5-position of the pentofuranose. Acetonation of ribonucleosides was shown to give the 2, 3 -C -isopropyl-idene derivatives, which were to become extensively used in nucleoside and nucleotide chemistry, and were utilized by Tipson in the first chemical preparation of a ribonucleotide, inosinic acid. 

The interdigital secretion of the red hartebeest, A. b. caama, consists of fewer compound classes. It contains a few alkanes and short-chain, branched alcohols, fatty acids, including a few of the higher fatty acids up to octadecanoic acid, an epoxide and the cyclic ethers, rans-(2 ,5.R)-furanoid linalool oxide 23, as-(2JR,5S)-furanoid linalool oxide 24 and ds-(2S,5i )-furanoid linalool oxide 25 (Fig. 5) in a ratio of 2.5 1 1.5 respectively [138]. From the point of view that many of the constituents of the interdigital secretion of this animal are probably of microbial origin, it is interesting that cis- and trans- furanoid linalool oxides have also been found in castoreum [77]. 

Tables V-LVII detail H and F shift and coupling information, and Tables LVIII to LXXI incorporate the C-n.m.r. data. The data within this compilation are arranged according to the following outline hexoses prior to pentoses, followed by anhydro sugars, sugar acids and lactones, amino sugars (and their synthetic, A -containing precursors), mono-, di-, and tri-deoxy sugars, branched derivatives, ketoses, polyfluorinated monosaccharides, and, finally, difluorinated amino sugars. Within this compilation, and even within each table, pyranoid derivatives are listed prior to their furanoid counterparts, hexoses prior to pentoses, functionalized prior to deoxy compounds the arrangement within each sub-table is made alphabetically.

Treatment of the selenide (19) with unbuffered 30% hydrogen peroxide-THF yields the cis- and trans-linalyl oxides (247) via [2,3] sigmatropic rearrangement. Kossanyi et al. have improved upon the efficiency of Vig s synthesis of the four lilac alcohols (248). The synthesis of the furanoid (249), formed during sulphuric acid-catalysed dimerization of isoprene, is straightforward. The known half-... 

Flavonols Foetidin Folic acid Folinerin Formononetin Forsythin Frangulin A Frangulin Fumaric acid Furanoid... 

Httero-Diels-Alder reactionAcrolein undergoes a Diels-Alder reaction with furanoid and pyranoid exocyclic vinyl ethers at 25 (4 6 days). The spirokelal (2) obtained can be oxidized in CHiOH by w-chloroperbenzoic acid to the ring... 

When applied to N-acylglycofuranosylamines, the periodate oxidation showed an abnormal uptake of oxidant ( overoxidation ). For example, when oxidized with lead tetraacetate12 and with periodate,1065 N-acetyl-a-D-glucofuranosylamine (15) afforded formaldehyde (indicating a furanose structure), and it consumed more than 5 moles of oxidant per mole. This result can be attributed to subsequent oxidation of the formic acid produced,69 or to the formation,10 by hydrolysis, of the intermediate 2-hydroxypropanedial (tartron-aldehyde) (77) that would then be oxidized. This tendency to undergo overoxidation has been found common for the furanoid N-acyl-gly cos y lam ines.24,25... 

The furanoid ring in benzo[6 ]furan is susceptible to attack by oxidants. Permanganate and chromic acid give derivatives of 2-hydroxybenzoic acid with compounds unsubstituted at the 3-position, but compounds with a 3-methyl or a 3-aryl substituent give derivatives of 2-hydroxyacetophenone or 2-hydroxybenzophenone. Ozonolysis of benzo[6]furan affords 2-hydroxybenzoic acid, 2-hydroxybenzaldehyde and some catechol produced via its diformate. Before the advent of NMR spectroscopy these methods were used in structural elucidation of benzofuranoid natural products, as in the case of O-methyleuparin (Scheme 26). 

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