Selective 1-O-Deacetylation of Carbohydrates Using Polymer-Bound Benzylamine

Abstract

A new method for highly effective and selective 1-O-deacetylation of peracetylated carbohydrates using polymer-bound amines is presented.

polymer-bound reagents - carbohydrates - deacetyl­ation - regioselectivity - protective groups

References

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15

Representative Experimental Procedure.
1,2,3,4,6-Penta-O-acetyl-β-d-glucopyranose (11 mg, 0.028 mmol) and aminomethylated polystyrene resin (60 mg, 0.90 mmol/g) were mixed in THF (1 mL) in a sealed tube. Then, Et₃N (0.011 mL, 0.0078 mmol) was added and the mixture was heated to 75 °C for 18 h. The mixture was filtered with CH₂Cl₂ and concentrated from CHCl₃. NMR showed 96% product and 4% starting material.

All compounds are commercially available except for

16a 2,3,4-tri-O-acetyl-d-xylopyranose: Utille J.-P. Gagnaire D. Carbohydr. Res.  1982,  106:  43 

16b 2,3,4,6-Tetra-O-acetyl-d-galactopyranose: Sim MM. Kondo H. Wong C.-H. J. Am. Chem. Soc.  1993,  115:  2260 

16c 2,3,6-Tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-d-galacto-pyranosyl)-d-glucopyranose: Ross AJ. Ivanova IA. Ferguson MAJ. Nikolaev AV. J. Chem. Soc., Perkin Trans. 1  2001,  72 

17

1,2,3,4,6-Penta-O-acetyl-β-d-glucopyranose (53 mg, 0.14 mmol) and aminomethylated polystyrene resin (288 mg, 0.90 mmol/g) were mixed in THF (5 mL) in a sealed tube. Then, Et₃N (0.05 mL, 0.0004 mmol) was added and the mixture was heated to 75 °C for 18 h. The mixture was filtered with CH₂Cl₂ and concentrated. The crude product was dissolved in CH₂Cl₂ (1 mL) and cooled to -10 °C under argon. Thereafter, Cl₃CCN (0.136 mL, 1.36 mmol) and DBU (0.005 mL, 0.033 mmol) were added and the reaction was allowed to reach r.t. and then stirred for 3 h. To this mixture DBU (0.005 mL, 0.033 mmol) was added and the composition was stirred for another hour and then concentrated and chromatographed (SiO₂, 1:1 heptane-EtOAc) to give 2,3,4,6-tetra-O-acetyl-d-glucopyranosyl trichloroacetimidate (57 mg, 85%). The product was in agreement with published data.

18 Cook BN. Bhakta S. Biegel T. Bowman KG. Armstrong JI. Hemmerich S. Bertozzi CR. J. Am. Chem. Soc.  2000,  122:  8612