MPEG-DOX

The final compound was isolated after peracetylation no trace of P-anomer was formed during the process. As in their first report, these authors also investigated the MPEG-DOX linkage of the first sugar residue via hydroxyl groups other than the anomeric one (Scheme 4.16). 

Using 5% Pd black, 1 atm H2 in ethanol at r.t. for 48 h, p-tolylmethyl derivative 74 was selectively obtained. Under stronger conditions (10% Pd/C, 50% aqueous AcOH, 3 atm H2 at 50°C) MPEG-DOX was completely cleaved to release, after acetylation, the derivative 75. This selective cleavage was reproduced using different... 

Scheme 4.15 Synthesis of D-mannopentaose from MPEG-DOX-OH using donor 6.

Scheme 4.16 MPEG-DOX linkage of the first sugar residue via nonanomeric hydroxyl groups.

Studying the influence of the activator and using the MPEG-DOX-OH support (Scheme 4.18),12 the same group reported the synthesis of trisaccharide 79 using donors 76 and 78 both glycosylations were performed by action of 3 equiv of donor, in the presence of 0.1 equiv of dibutylboron triflate (DBBOTf) as activator and 4-A molecular sieves at -45°C for 30 min. 

Glycosylation of MPEG-DOX-OH with 76 was achieved in 95% yield. After deacetylation using DBU in methanol, glycosylation using disaccharide donor 78 was performed and resin-linked trisaccharide was obtained in 85% yield. 

G. Hodosi and J. J. Krepinsky, Polymer-supported solution synthesis of oligosaccharides Probing glycosylation of MPEG-DOX-OH with 2-acetamidoglycopyranosyl derivatives, SYNLETT, (1996) 159-161. 

The MPEG-DOX grouping is readily synthesized from MPEG-OH and a,a -dichloro-p-xylene by Williamson ether synthesis yielding MPEG-DOX-Cl, and, after hydrolysis, the alcohol MPEG-DOX-OH [54]. MPEG-DOX-OH can be... 

The attachment of MPEG-DOX to a carbohydrate hydroxyl other than the anomeric one is achieved by the reaction of such hydroxyl with MPEG-DOX-Cl by... 

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