A general synthetic route for the preparation of the first analogue of a new series of sugar-modified C-nucleoside phosphonates is detailed. Such derivative contains a fourcarbon L-threose sugar moiety substituted with a phosphonomethoxy group at the 3′-position and pyrrolo[2,1-f ][1,2,4]triazin-4-amine as nucleobase. A C-nucleoside was initially prepared by coupling a benzyl protected L-threono-1,4-lactone intermediate with the corresponding aglycon moiety. The choice Eur.General Information: For all reactions, analytical grade solvents were used. All moisture sensitive reactions were carried out in ovendried glassware (120°C) under a nitrogen or argon atmosphere.