Perbenzylated a-glycosyl

The perbenzylated a-glycosyl iodides are thought to react with oxetane via the mechanisms shown in Schemes 21 and 22 (where R=PhCH2).138 The amount of the -product increases as the reaction temperature decreases. In fact, at — 60 °C, the fi a ratio in the product from the perbenzylated derivatives of galactosyl, mannosyl, and glucosyl iodides ranges from 10 1 to 50 1, indicating that the reaction in Scheme 21 is faster than that in Scheme 22. 

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