s independently H or phosphate; R6 is an alkyl, halogeno-alkyl (i.e. CF3), alkenyl, or alkynyl (i.e. allyl); and X is O, S, SO2 or CH2 can be prepared by one of the following general methods. 1 Glycosylation of the Nucleobase with an Appropriately Modified Sugar The key starting material for this process is an appropriately substituted sugar with a 3???-OH and 3???-H, with the appropriate leaving