An Efficient Synthetic Route for a Versatile Ciliapterin Derivative and the First Ciliapterin D-Mannoside Synthesis

The key precursor, N(2)-(N,N-dimethylaminomethylene)-1’-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]ciliapterin (15) was efficiently prepared from D-xylose via an improved route. The first synthesis of 2’-O-(α-D-mannopyranosyl)ciliapterin (2c) was achieved by treatment of 15 with 2,3,4,6-tetra-O-benzoyl-α-D-mannnopyranosyl bromide in the presence of silver triflate and tetramethylurea, followed by removal of the protecting groups.