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.