A New Protocol for Selective Cleavage of Acyl Protecting Groups in 2′-O-Modified 3′,5′-O-(Tetraisopropyldisiloxane-1,3-diyl)ribonucleosides

The stability of tetraisopropyldisiloxane-1,3-diyl (TIPDS) protection in nucleosides in ammonia/amine solutions in methanol and ethanol was studied. In ammonia-methanol at ambient temperature significant partial cleavage of TIPDS was observed. When ethanol was used instead of methanol this undesired side reaction was completely inhibited. It was found that commercially available 8 M methylamine-ethanol solution is the reagent of choice for selective deacylation of N- or/and O-acyl protected nucleosides without notable cleavage of 3',5'-TIPDS group. Several examples of the developed protocol for the preparation 2'-O-modified nucleosides with overall high yields are presented.