Chemical Synthesis of the Antiviral Nucleotide Analogue ddhCTP

3′-Deoxy-3′,4′-didehydro-cytidine triphosphate (ddhCTP) is a novel antiviral molecule produced by the enzyme viperin as part of the innate immune response. ddhCTP has been shown to act as an obligate chain terminator of flavivirus and SARS-CoV-2 RNA-dependent RNA polymerases; however, further biophysical studies have been precluded by limited access to this promising antiviral. Herein, we report a robust and scalable synthesis of ddhCTP as well as the mono-and diphosphates ddhCMP and ddhCDP, respectively. Identification of a 2′-silyl ether protection strategy enabled selective synthesis and facile purification of the 5′-Triphosphate, culminating in the preparation of ddhCTP on a gram scale.