Fructose 1,1-dimethyl

Di-O-methyl-D-glucose and thence the corresponding dimethyl-D-fruc-tose was produced from l,2-0-isopropylidene-6-0-triphenylmethyl-a-D-glucofuranose and purified by way of its a-1,2,6-triacetate, catalytic treatment of which, with sodium methoxide, gave the 6-acetate. Reaction with a stronger solution of this reagent afforded the fructose dimethyl ether. 1,6-Anhydro-... 

Two methylations of levan by means of dimethyl sulfate and potassium hydroxide (not sodium hydroxide) followed by one inethylation with methyl iodide and silver oxide yielded trimethyllevan in 88% yield. This was purified by solvent fractionation over-all yield 75%, m. p. 145-146°, OCHs 45.9%. Trimethyllevan, hydrolyzed by heating at 95° for twenty-four hours with a dilute solution of sulfuric acid gave a 98.5% yield of a crystalline trimethyl-D-fructose. The trimethyl-D-fructose was proved940 to be 1,3,4-trimethyl-D-fructofuranose since oxidation with nitric acid gave a 97% yield of a dimethyl-2-keto-D-gluco-saccharic acid which was identified as the crystalline diamide (95% yield). 

Haworth, Hirst and Percival23 methylated inulin by first acetylating and subsequently converting the acetate to the methyl derivative by means of dimethyl sulfate and sodium hydroxide in acetone solution, a procedure described by Haworth and Streight.24 They hydrolyzed trimethylinulin and quantitatively determined the amounts of trimethyl-D-fructose and tetramethyl-D-fructose formed. There was obtained 3.7%... 

It is believed by Schlubach and Sinh35 that the polyfructosans are, as a rule, made up of D-fructose residues joined in a ring. According to these authors, when the methyl derivatives of the polysaccharides are hydrolyzed, the amounts of dimethyl- and tetramethyl-D-fructose formed... 

The acetate was dissolved in acetone and converted to the methyl derivative by the use of dimethyl sulfate and sodium hydroxide. After three methylations, a product containing 45.6% OCHa was obtained. Hydrolysis yielded dimethyl-, trimethyl-, and tetramethyl-D-fructose in the ratios (calculated as D-fructose) of 1 8 1. The trimethyl-D-fructose... 

Methylation was carried out according to the procedure of Haworth and Streight.24 Trimethylphlein has m. p. 172°, [o ]d20 = — 57.7° (c = 1.0, chloroform), average molecular weight 3280. Upon hydrolysis, 1,3,4-trimethyl-D-fructose resulted accompanied by a small amount of dimethyl-D-fructose which could be accounted for by the slightly low... 

Secalin. Secalin has been isolated from the stems of unripe rye.46,68 Schlubach and Bandmann69 studied its structure. The great difficulty they encountered in obtaining the polysaccharide and its acetate in homogeneous form made the determination of physical properties uncertain. However, by hydrolysis of the methyl derivative, they obtained, after separation by means of the /3-naphthoates, tetramethyl-, trimethyl-, and dimethyl-D-fructoses in the proportions of 1 2 1. The trimethyl-D-fructose was identified as 1,3,4-trimethyl-D-fructofura-nose by its melting point and specific rotation. 

Upon hydrolysis an equal amount of tetramethyl-D-fructose and dimethyl-D-fructose was obtained. The first of these was identified as 1,3,4,6-tetramethyl-D-fructose by conversion to the characteristic crystalline acid amide obtained by Haworth, Hirst and Nicholson.66 The dimethyl-D-fructose was obtained as a thick brown sirup having [oT]d20 = + 20.0° (c = 1.82, chloroform). 

From these results the authors conclude that irisin is composed of a series of D-fructose units, each member having an additional D-fructose molecule attached. The tetramethyl-D-fructose is thus derived from these dangling D-fructose units. The position of the unions in the rest of the molecule has not been ascertained since the structure of the dimethyl-D-fructose is unknown. 

The ultraviolet absorption spectra of compounds II from D-glucose and XI from D-fructose show an absorption band at 250 m/j, in accordance with their furan character.9 The product of periodate oxidation (V) and the dimethyl ester of the derived dicarboxylic acid (III) absorb at 285 and 262 m/i, respectively. The anhydrides of the condensates, XXXIV, do not exhibit selective absorption in the ultraviolet region, but the product of their oxidation (XXXVI) with periodic acid shows8 a band at about 270 m/i. 

HTAC and HTAH have been used as surfactants in the chemiluminescence reaction of lucigenin (10,10 -dimethyl-9,9 -biacridinium dinitrate) with biological reductants (such as fructose, glucose, ascorbic and uric acid) or hydrogen peroxide [38],... 

One of the few zwitterionic surfactant used in CL reactions is /V-dodccyl-MA-dimethyl-ammonium-3-propane-l-sulfonate (SB-12). Particularly, SB-12 has been assayed in the study of the CL reaction of lucigenin with various biological reductants [10]. The results show that SB-12 enhances CL intensity of the luci-genin-glucose and lucigenin-fructose systems by factors of 3.0 and 1.5, respectively, compared to the intensity obtained in aqueous medium. In these conditions detection limits were found for-both analytes of 0.7 X 10 4 and 2.5 X 10 5 M, respectively. 

Recently Cavaleiro et al. described an easy synthetic approach to glycoporphyrins from zinc(n) protoporphyrin-IX dimethyl ester 4 and O-allyl carbohydrate acetonides 5A-E (D-ribose (A), D-galactose (B), D-glucose (C), and two isomeric derivatives (D) and (E) of D-fructose) by cross-metathesis (Scheme 2).12 Two equivalents of each carbohydrate and the Grubbs catalyst were used, giving the carbohydrate derivatives 6 in a range of 74% to 93% yields. 

Amino-1-deoxy-D-fructose acetate was reacted with dimethyl methoxymethylenemalonate in the presence of sodium carbonate in water at ambient temperature for 4 hr to give aminomethylenemalonate (19) in 97% yield several isomeric forms were present both in the solid state and in solution (86MI10) (see Table IV and Scheme 5B). 

Several products were also detected in base-degraded D-fructose solution acetoin (3-hydroxy-2-butanone 62), l-hydroxy-2-butanone, and 4-hydroxy-2-butanone. Three benzoquinones were found in the product mixture after sucrose had been heated at 110° in 5% NaOH these were 2-methylbenzoquinone, 2,3,5-trimethylbenzoquinone, and 2,5-dimethyl-benzoquinone (2,5-dimethyl-2,5-cyclohexadiene-l,4-dione 61). Compound 62 is of considerable interest, as 62 and butanedione (biacetyl 60) are involved in the formation of 61 and 2,5-dimethyl-l,4-benzenediol (63) by a reduction-oxidation pathway. This mechanism, shown in Scheme 10, will be discussed in a following section, as it has been proposed from results obtained from cellulose. 

The results of a detailed study of D-fructose and five O-glucosyl-substi-tuted D-fructoses17 confirmed that increasing the temperature increases the proportion of the furanose forms. This effect is much more noticeable in water and in pyridine than in dimethyl sulfoxide. In other ketoses, the proportion of the keto form also increases with increasing temperature.12... 

F. W. Lichtenthaler and S. Ronninger, a-D-Glucopyranosyl-D-fructoses Distribution of fur-anoid and pyranoid tautomers in water, dimethyl sulphoxide, and pyridine. Part 4. Studies on ketoses, /. Chem. Soc., Perkin Trans, 2 (1990) 1489-1497. 

Another interesting example of hindered internal rotation is related to the relative stability of the /3-furanose form of D-fructose (12a) in dimethyl sulfoxide solutions,83139-141 in marked contrast to the fact that the /3-pyranose form (13) is by far the predominant tautomer in water. From the, 3C 7, relaxation data83 (see Table HI) of the three major tautomers of D-fructose—a-furanose (12b), jS-furanose (12a), and 0-pyranose (13)—it can be concluded that these tautomers tumble isotropically in both D20 and (CD3 )2SO solutions. The T, values83 for the second-... 

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