Acylation of 2′,3′,5′-tri-O-acetylguanosine

2′,3′,5′-Tri-O-acetylguanosine (1b) reacts with 2,6-dichlorobenzoyl and mesitylenesulphonyl chlorides to give the corresponding crystalline O(6)- acyl derivatives [(2) and (3a), respectively].