Preparation of glycosylated amino acids

IT-(9-FluorenylmethoxycarbonyO-L-aspartic acid -3,4-dihydro-4-oxobenzotriazin-3-yl ester a-tert-butyl ester (13) 

Dicyclohexylcarbodiimide (DCC, 376 mg, 1.82 mmol) was added to a solution of W -(9-fluorenylmethoxycarbonyl)-L-aspartic acid te/t-butyl ester (12, 750 mg, 1.82 mmol) in freshly distilled THF (10 ml) at -35 C. After 10 min DhbtOH (298 mg, 1.82 mmol) was added and the mixture was stirred for a further 2 h before being allowed to attain room temperature. Then the mixture was filtered through Celite and concentrated. The residue was dissolved in THF (7.5 ml), filtered again through Celite and concentrated. Flash column chromatography on Si02 (heptane/EtOAc, 4 1) gave 13 (890 mg, 88%). 

2-Acetamido-4-0-(2-acetamido-2-deoxy- -D-glucopyranosyl)-2-deoxy- -D-glucopyranosyl amine (IS) 

NH4HCO3 (s) was added to 2-acetamido-4-0-(2-acetamido-2-deoxy-p-D-glucopyranosyl)-2-deoxy-p-D-glucopyranose (14, 200 mg, 470 p.mol. Sigma, Missouri, USA) at 45°C in DMSO (50 ml) until a saturated solution was obtained. Portions of NH4HCO3 (s) were added frequently to the mixture during 30 h to ensure saturation. 

Conversion of 14 into 15 was monitored by H NMR spectroscopy in DMSO-de. When conversion was complete the solution was lyophilized to give crude 15 which was used directly in the next step. 

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Preparation of Glycosylated Amino Acids Suitable for Fmoc Solid-Phase Assembly... 

S. Manabe, K. Sakamoto, Y. Nakahara, M. Sisido, T. Hohsaka, Y. Ito, Preparation of glycosylated amino acid derivatives for glycoprotein synthesis by in vitro translation system, Bioorg. Med. Chem. 2002, 10, 573-581. 

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