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Compound 26 (624 mg, 1.41 mmol; wherein R, R'=OH; Sigma) was dissolved in H2O (15 mL), applied to a Bio-Rad AG 50W-X2 cation exchange column (Et3N+, 2.5×8 cm), and eluted with H2O (150 mL). The solution was evaporated, coevaporated with MeOH (2×10 mL) and dried for 3 d under vacuum to give triethylammonium β-L-fucopyranosyl phosphate 29 (512 mg). The content of triethylamine was determined to be 1.16 equiv. (1H NMR) A mixture of 29 (57.5 mg, 159 μmol) and guanosine 5'-monophospho morpholidate 4-morpholine-N,N'-dicyclohexylcarboxamidine salt 27 (201 mg, 255 μmol) was coevaporated with dry pyridine (3×1.5 mL). 1H-Tetrazole (33 mg, 477 μmol) and dry pyridine (0.8 mL) were added, and the solution stirred at rt. After a while, product starts to precipitate. The reaction was monitored by TLC (2:1 i-PrOH/1M NH4OAc). After 2 d, the mixture was diluted with water (1.5 mL) to become a clear solution, evaporated, and coevaporated with water (2×1.5 mL). The residue was purified on a Bio-Gel P-2 column (2.5×70 cm), eluated with 250 mM NH4 HCO3 to give 30 (82.4 mg, 85%) as a white solid after lyophilization (Rf 0.43, 2:1 i-PrOH/1M NH4OAc). The 1H NMR spectral data were in agreement with the published ones (Nunez et al. Can. J. Chem. 1981, 59, 2086-2095; Gokhale et al. Can. J. Chem. 1990, 68, 1063-1071).

1. customto precipitate
2. additionthe mixture was diluted with water (1.5 mL)
3. customevaporated
4. customThe residue was purified on a Bio-Gel P-2 column (2.5×70 cm)