chapter  25
10 Pages

Synthesis of Methyl 4-azido-2,3-di-O-benzoyl-4-deoxy-α-l- arabino-pyranoside

Experimental Methods ........................................................................................... 194 General Methods ............................................................................................... 194 Methyl 4-O-p-Toluenesulfonyl-β-d-xylopyranoside (2) ................................... 194 Methyl 2,3-di-O-Benzoyl-4-O-p-toluenesulfonyl-β-d-xylopyranoside (3) ...... 195 Methyl 4-Azido-2,3-di-O-benzoyl-4-deoxy-α-l-arabinopyranoside (4) .......... 195

Acknowledgments .................................................................................................. 196 References .............................................................................................................. 201

graphic purication.3 In an alternative approach, the conversion of an intermediate 3,4-O-stannylene acetal into tosylate 2 is near quantitative.4,5 Benzoylation of 2 produces crystalline 3 in 95% yield. Subsequent azide introduction can be accomplished at 90°C and 15 h reaction time or by increasing the reaction temperature to 110°C (safety shield required!) within 2.5 h, which provides the target compound 4 in high (91%) yield.6 Compound 4 is a versatile precursor for Ara4N glycosides via transglycosylation of the methyl glycoside and allows easy transformation into variably protected Ara4N glycosyl donors.7