Haworth methylation

Haworth methylation of methyl /3-D-glucopyranoside and its 4-benzyl and 4-(tetrahydropyran-2-yl) ethers was investigated in connection with partial-methylation studies on cellulose.267 For the unsubstituted glycoside, the ratios of relative rate-constants k2 k3 k4 k were estimated to be 8 2 1 8, and, for the 4-ethers, it was found that ke> k2> k3 best agreements between calculated and experimental yields were found with the assumption that the rate constant for reaction at HO-3 is doubled when HO-2 is substituted. Later methylation studies,268 performed to low degrees of substitution, with analysis by gas-liquid chromatography, gave k2> k4> k3 for the reactivity... 

This sugar was first prepared by Irvine and Moodie48 by the methyla-tion of methyl a-D-mannopyranoside with methyl iodide and silver oxide in the presence of methanol as solvent. The crystalline methyl tetra-methyl-a-D-mannoside yielded, on acid hydrolysis, sirupy 2,3,4,6-tetra-methyl-D-mannose. Methylation has been carried out subsequently using dimethyl sulfate and sodium hydroxide49 60 and by the reaction of the potassium salt of methyl a-D-mannopyranoside with methyl iodide in liquid ammonia.61 The Haworth methylation procedure has also been... 

Haworth methylation. Formation of methylated methyl glycosides from monosaccharides with dimethyl sulfate and 30% sodium hydroxide. The glycosidic methyl group is hydrolyzed with acid to yield the free methylated sugar. 

The exhaustive Haworth methylation with dimethyl sulfate in alkaline medium, with retention of configuration at the anomeric carbon atom... 

Other references related to the Haworth methylation are cited in the literature. ... 

This reaction has been modified to become the Haworth Methylation, which was extended to treat sugars with sodium methylsulfinyl carbanion and methyl iodide for the purpose of per-O-methylation in one step7 ... 

Haworth Methylation Haworth Phenanthrene Synthesis Hayashi Rearrangement Heck Reaction Helferich Method Hell-Volhard-Zelinsky Reaction Henkel Process Henkel Reaction Henry Reaction... 

This formula was confirmed hy Haworth and Perkin s synthesis of a-flZZocryptopine from herherine, the first application of a process, of which examples have heen given already in the syntheses of cryptopine (p. 298) and protopine (p. 301) hy the same authors. Anhydrotetrahydromethyl-herherine (I cf. hase (a), p. 346) in dry chloroform was added to a solution of perhenzoic acid in ether cooled helow 5°. The amine oxide, C21H23O5N (II), separated as an oil, which after shaking with sodium hydroxide solution, solidified and was crystallised from water in slender prisms, m.p. 135°. It was dissolved in acetic acid, hydrochloric acid added, the mixture heated in boiling water for an hour and the hase precipitated hy addition of potassium hydroxide. The precipitate was dissolved in methyl alcohol, ether added, the alcohol washed out with water and the ethereal... 

Stacey started research in an inspiring and stimulating atmosphere that he strove to maintain, add to, and develop when it became his turn to lead the department. His earliest research was with Haworth and his key partner E. L. Hirst [Adv. Carbohydr. Chem. Biochem., 35 (1978) 1 -29] on aspects of the chemistry of glucoheptose. His first publication with them in 1931 was entitled Walden Inversion in the a-Glucoheptose Series, followed in the next year by a report on the methylation of monocarboxylic acids derived from aldoses and the structure of pentamethyl a-gluco-heptonolactone. He found this to be a difficult project because, initially, he could not crystallize his stock of glucoheptose. Then, as later, he found crystallization to be a challenging problem. 

Methylation of Monocarboxylic Acids Derived from Aldoses. Structure of Pentamethyl a-Gluco-heptono-y-lactone, W. N. Haworth, E. L. Hirst, and M. Stacey, J. Chem. Soc., (1932) 2481-2485. 

When this paper11 was published (in 1938), the evidence indicated that the hydrofuranol ring compound isolated was the pyranoside form (XLVI). The later work of Haworth, Owen, and Smith,28 which is discussed in section V-l, corrected this impression and proved that the compound actually isolated by Peat and Wiggins was methyl 3,6-anhydro-/3-D-glueofuranoside (XLVIII). This correction does not invalidate the above argument, for it is known that XLVI is unstable and a trace of acid suffices to transform it into the stable furanoside. 

Both methods of approach moreover proved that a series of methylated derivatives of D-glucosamine described by Cutler, Haworth and Peat,14 and most useful as reference compounds in this field, were all of the pyranose configuration. Further proof of the pyranose structure of methyl D-glucosaminide and methyl N-acetyl-D-glucosaminide was pro-... 

Challinor, Haworth and Hirst101 determined the chemical structure of the levan produced by the action of B. mesentericus on sucrose. Methylated levan appeared homogeneous when fractionally precipitated from mixed solvents. Fractional distillation of the hydrolytic products of methylated levan yielded tetramethyl-D-fructofuranose in an amount corresponding to a levan chain length of from ten to twelve fructofuranose units, joined as previously940 shown through the 2- and 6-positions. 

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%... 

A large number of polyfructosans that have been reported from time to time by different authors have been investigated by Schlubach and his associates. In order to obtain polysaccharides of constant optical rotation, 100 to 300 precipitations from aqueous solution by the addition of alcohol were necessary. Fifty to 150 precipitations from chloroform solution with petroleum ether were required for purification of the acetate derivatives. These were methylated according to the procedure of Haworth and Straight,24 and upon hydrolysis partially methylated fructoses were obtained. 

---