any degradation.

4.1.2  General method A for the synthesis of compounds 18, 26, 27 and 29
To a solution of 5′-amino-2′,3′-isopropylidene adenosine in anhydrous DMF (conc. 0.2 M) was added Et3N (2.00 eq) and the corresponding nitrobenzenesufonyl chloride (1.50 eq) at 0