Abstract
A convenient method for the selective differentiation of the 2-OH and 3-OH of pyranosides, based on the CsO2 CCF3 - or Ag2 O-mediated acyl migration, has been established. The 2-OH and 3-OH can be sequentially glycosylated by the desired carbohydrate generating disaccharides of biological interest. A mechanism involving either acid- or base-assisted acyl migration is proposed.
Key words
ABO blood group antigens - silver oxide - cesium trifluoroacetate - acyl migration - migration mechanisms
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15
Acyl Migration Using Ag
2
O; General Procedure . A solution of starting material (0.12 mmol) and TBAI (4.2 mg, 0.012 mmol), Ag2 O (0.12 mmol) in anhyd DMF (5 mL) was stirred at the indicated temperature. The reaction was monitored by TLC. When the side product appeared, the reaction mixture was subsequently filtered then concentrated. The filtrate was subject to flash column chromatography to yield the desired product. The unreacted starting material was recovered.
16
Acyl Migration Using CsO
2
CCF
3
; General Procedure . A mixture of starting material (0.20 mmol), CsO2 CCF3 (0.20 mmol), and TBAI (8 mg, 0.02 mmol) in anhyd DMF (10 mL) was stirred at the indicated temperature. The reaction was monitored by TLC. When the side product appeared, the reaction mixture was filtered then concentrated. The filtrate was subject to flash column chromatography to yield the desired product. The unreacted starting material was recovered.
