Synthesis of Nucleoside Polyphosphates and their Conjugates
Mohamady Mohamady, Samy
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Nucleoside polyphosphates and their conjugates, such as nucleoside triphosphates, nucleoside tetraphosphates, sugar nucleotides, dinucleoside pyro- and higher order polyphosphates, 2’,3’-cyclic nucleoside monophosphates, and 2´-deoxynucleoside-5´-tetraphosphates in which a fluorescent label is attached to the terminal phosphate have many biological roles and have been developed into drugs. However, their synthesis remains a challenge. Several novel and efficient approaches to the synthesis of nucleoside polyphosphates and their conjugates were developed. In the first approach dinucleoside polyphosphates (NpnN’s where n = 2-4) are prepared via in situ trifluoroacetate protection and imidazolium activation of nucleoside 5’-monophosphates. This methodology was also used to prepare a substrate-intermediate analog of the reaction catalyzed by cytidine triphosphate synthase (CTPS) a recognized target for the development of antineoplastic, antiviral and antiprotozoal agents. The second approach uses sulfonylimidazolium salts as key reagents for generating highly reactive nucleotide donors. The procedure is rapid, produces a wide variety of nucleoside polyphosphates and their conjugates in high yield, does not require protection and subsequent deprotection of the nucleotide donors or acceptors and can be used to activate nucleoside mono-, di-, and triphosphates and a wide variety of acceptors. Finally an entirely new approach to the synthesis of nucleoside tetraphosphates (Np4’s), dinucleoside pentaphosphates (Np5N’s) and nucleoside tetraphosphates in which a fluorescent dye is attached to the terminal phosphate is described employing an activated form of cyclic trimetaphosphate as a novel phosphorylating agent. Attempts to prepare nucleoside triphosphates by subjecting unprotected ribonucleosides and 2’-deoxyribonucleosides to activated cyclic trimetaphosphate failed. Instead nucleoside 2’,3’-cyclic phosphates were obtained in good yield with the ribonucleoside substrates. This represents a new and convenient approach to the synthesis of this class of compounds.