Provided are methods of preparing compounds and pharmaceutical compositions comprising a compound Formula VIII for treating Filoviridae virus infections. In one aspect, the compound of Formula VIII is formed from a reaction mixture comprising the compound of Formula IX, the compound of Formula X, a coupling agent such as magnesium chloride and a non-nucleophilic base such as diisopropylethylamine. The compound of Formula IX can be formed from a compound of Formula V and a cyanating agent. The compound of Formula V can be synthesized from a reaction mixture comprising a deprotonating agent such as phenylmagnesium chloride; a silylating agent such as chlorotrimethylsilane; a coupling agent such as isopropylmagnesium chloride, an additive such as LaCl3-2LiCl, LaCl3, CeCl3, NdCl3, or YCl3; a compound of Formula VI; and 7-iodopyrrolo[2,1-f][1,2,4]triazin-4-amine. The compounds, compositions, and methods provided are particularly useful for the treatment of Marburg virus, Ebola virus and Cueva virus infections.