Protected dinucleoside-2',5'-monophosphate has been prepared to develop a prodrug strategy for 2-5A. The removal of enzymatically and thermally labile 4-(acetylthio)-2-(ethoxycarbonyl)-3-oxo-2-methylbutyl phosphate protecting group and enzymatically labile 3'-O-pivaloyloxymethyl group was followed at pH 7.5 and 37 °C by HPLC from the fully protected dimeric adenosine-2',5'-monophosphate 1 used as a model compound for 2-5A. The desired unprotected 2',3'-O-isopropylideneadenosine-2',5'-monophosphate (9) was observed to accumulate as a major product. Neither the competitive isomerization of 2',5'- to a 3',5'-linkage nor the P-O5' bond cleavage was detected. The phosphate protecting group was removed faster than the 3'-O-protection and, hence, the attack of the neighbouring 3'-OH on phosphotriester moiety did not take place.
Keywords: 2-5A; Deprotection; Nucleotides; Prodrugs; Protecting group.
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