prov:value
| - When R8 is not a participating group, such as OH, SH, NHR (R is methyl, ethyl, isopropyl or benzyl), 18 is treated with mesyl chloride in pyridine to afford the di-O-mesylate 19, which is converted into the 2???,5???-di-O-acyl arabino derivative 20 by treatment with alkali metal acylate, such as potassium acetate or sodium benzoate, preferably potassium acetate, in a polar solvent, such as dimethy
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