Methyl a-glucopyranoside

S. Signorella, M. I. Frascaroli, S. Garcia, M. Santoro, J. C. Gonzalez, C. Palopoli, V. Daier, N. Casado, and L. F. Sala, Kinetics and mechanism of the chromium(VI) oxidation of methyl-a-glucopyranoside and methyl-a-D-mannopyranoside,./. Chem. Soc. Dalton Trans. (2000) 1617-1623. 

Figure 4.29 75 MHz NMR spectrum of methyl a-glucopyranoside in a mixture of CDCI3 and DMSO-cfe Sc CDCI3 79.8 (three peaks), Sc DMSO-de 40.5 (not shown)...

Figure 4.38 75 MHz DEPT 135 spectrum of methyl a-glucopyranoside in DMSO-de...

Separation selectivity can also be altered by the type of ion that is formed for the compound of interest. Cation or anion adducts can have a significant effect on the separation. In the positive ion mode, most ions formed from electrospray or any chemical ionization methods are protonated cations. However, if Na+ is added to the electrospray solution, sodiated adducts may be formed as the primary response ion. For example, the protonated ions of two isomers, methyl-P-glucopyranoside and methyl-a-glucopyranoside, cannot be baseline separated in DTIMS, but the sodiated adducts of the same isomers can be baseline separated. Figure 8.9 demonstrates separation selectivity induced by cation adduction. These IMS spectra are of the methyl-p-D-galactopyranoside and the methyl-a-D-galactopyranoside isomers adducted with cobalt acetate, silver, and lead acetate. The cobalt acetate adducts had a separation factor of 1.02, the silver adducts had a separation factor of 1.05, and the lead acetate adducts had a separation factor of 1.07. 

Tetraalkylammonium salts have been used as phase transfer catalysts for alkylation [5], sulfonylation [46], and benzoylation reactions [47] of carbohydrate derivatives in mixed organic/aqueous solvent. For example, benzyhdene-protected methyl a-glucopyranoside underwent selective benzylation at the more acidic 2-OH group in the presence of a phase transfer catalyst (Scheme 11). 

Scheme 12 Selective oxidation of methyl a-glucopyranoside using TEMPO as a pre-catalyst...

Scheme 31 Palladium-catalyzed, regioselective oxidation of methyl a-glucopyranoside. DCB denotes 2,6-dichloro-1,4-benzoquinone...

Our initial studies were directed towards the synthesis and characterization of phenylboronate esters derived from methyl 6-deoxy-/ -D-allopyranoside, methyl a-L-rhamnopyranoside, methyl -L-fucopyranoside, and methyl 6-deoxy-/ -D-glucopyranoside. Previous work (14) in this laboratory indicated that the reaction of triphenylboroxole and methyl... 

A mixture of d- and l- hexoses also results from the hydroboration of these 5-enes. Hydroboration results in anti-Markownikoff, cw-hydration of the double bond and the amount of each hexose formed varies according to the nature of the substituent groups. For example, hydroboration (23) of methyl 6-deoxy-a-D-ryZo-hex-5-enopyranose (3) affords methyl a-D-glucopyranoside and methyl / -L-idopyranoside in the ratio of 1 2.5 respectively whereas hydroboration of the fris-trimethylsilyl ether of 3 afforded them in the ratio 1 0.6 respectively. The hydroboration method can be used to achieve specific labelling of hexoses with tritium methyl-/ -L-idopyranoside[5-H3] and methyl a-D-glucopyranoside [5-H3] were thus prepared (23). Similarly, hydroboration of the D-Zt/ro-hex-5-eno derivative (14) with diborane-H3 followed by removal of the isopropyli-dene group, afforded methyl a-D-mannopyranoside [5-H3] and methyl / -L-gulopyranoside [5-H3] in the ratio of 1 2 respectively (23). 

Sinclair (92) has described an improved method for the preparation of methyl 6-chloro-6-deoxy- -D-glucopyranoside (137) from methyl a-D-glucopyranoside (11). The reaction was effected with sulfur monochloride S2C12 in N,N-dimethylformamide at room temperature and the... 

Methyl a-D-glucopyranosid-4-0-yl)pyruvic acid [or methyl 4-0-(oxalomethyl)-a-D-glucopyranoside]... 

Methyl (3-0-acetyl-6-deoxy-2,4-di-0-methyl-a-L-galactopyranosyl)-(1->4)-(allyl 2,3-di-Obenzoyl-p-D-glucopyranosid)uronate... 

Spectrum (- -), and Fragment Circular Dichroism Spectra (—) for the Corresponding d-Xylose and the Addition of a Hydroxymethyl Group at C-S (a) a-o-Glucose (b) /3-D-Glucose (c) Methyl a-o-Glucopyranoside and (d) Methyl /8-D-Glucopyranoside. (Redrawn from Ref. 

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