A NEW SYNTHESIS OF Β-Glucopyranosides

Abstract

Reaction of equivalent amounts of pentaacetyl-P-D-glucopyranose and methanol in benzene or chloroform solution in the presence of 0.5 or more moles of stannic chloride oer mole of methanol pave 50-60Yn vields of methvl tetra-acetyl-8-u-gl~~copyranosidc. a-Xcetocl~lorogl~~cose was ;I by-protltlct of thc rcaction. The mechanisn~ of the reaction is disct~ssed. 'l'he n~etl~otl was applicaClle for the preparation of phenyl tetraacetyl-13-D-glucopyranoside. INTRODUCTIONLemieux and Brice (3) have shown that the treatment of pentaacetyl-0-Dglucopyranose (I) with stannic chloride in chlorofornl solutiol~ resulted in a rapid dissociation of the C1 to acetoxy group bond to yield carbonium ions of which the resonance stabilized 1,2-cyclic ion (11) is the predominant type. Treatment of 1,2,3,4-tetraacetyl-/3-D-glucose under these conditions yielded the internal glucoside, triacetyl-D-glucosan (1,5) P (1, 6) (3). Thus, it was reasonable to expect that treatment of pentaacetyl-/3-D-glucopyranose with stannic chloride in cl~loroform containing an alcohol \srould lead to glucoside formation. Since the ion I1 would predominate and the reaction of this ion with the alcohol under the ,prevailing acidic conditions would be accon~panied by an inversion of the anomeric center, it was expected that the initial reaction 0-0-0-HC-OAcproduct would be the acetylated P-D-glucopyranoside (111). Since pentaacetyl-P-~glucopyranose was found to be rapidly dissociated by stannic chloride (3), it was anticipated that the p-glucoside would be fonned rapidly a t the boiling point of the reaction mixture. Pacsu (8) has shown that stannic chloride can catalyze the anomerization of methyl tetraacetyl-p-D-glucopyranoside only slowly. Consequently, it was expected that the reaction of pentaacetyl-P-D-glucopyranose with methanol in the presence of stannic chloride would afford a good yield of methyl tetraacetyl-P-D-glucopyranoside. Lindberg (5) has shown that the rate of anomerization of a P-glucopyranoside depends greatly on the nature of theaglucon.

Reliable method for the synthesis of aryl β-D-glucopyranosides, using boron trifluoride–diethyl ether as catalyst

“…Jeffrey et al 21 and others 22 reported that the temperature at which the glucosylation is carried out determines the configuration at the anomeric centre. Using SnCl 4 as the promotor, they obtained the aryl β-D-glucopyranosides under conditions of kinetic control at 20 °C and the thermodynamically more stable α-anomer when the reaction temperature was 40 °C.…”

THE ALPHA AND BETA 1,3,4,6-TETRAACETYL-D-GLUCOPYRANOSES AND THEIR CHLOROACETYL DERIVATIVES

“…137-13S°C., [a]D +26" (chloroforln). The structures of these glucose tetraacetates were established by the interconversion of chloroacetyl derivatives.Our studies of the properties of the pentaacetylglucopyranoses (16,17,18) have established the strong activating effect of C2-acetoxy group participation in dissociation of the C1 to acetoxy group bond of the 1,2-trans-p-anomer. I t was now of interest to examine the effect of altering the C2-substituent on the ease of dissociatioll and for this the anomeric 1,3,4,6-tetraacetyl-D-glucopyranoses were desirable starting materials.…”

Synthesis of Glycocinnasperimicin D

“…Although synthesis of aryl a-glycopyranosides and isomerization of the phenyl b-glycopyranosides into the a-isomers (anomerization) have been described, [28] the yields of the reported procedures are relatively low (23-32 %). In contrast, b-selective syntheses of phenyl glucosides [29] and galactosides [30] are well documented. Prompted by these earlier reports, preliminary investigations began with the Lewis acid catalyzed glycosylation of phenol with penta-O-acetyl-d-galactopyranoside 33 to obtain the b-anomer 35 (Scheme 8).…”