First synthesis of tepidopterin [2′-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-l-threo-biopterin]

N2-(N,N-Dimethylaminomethylene)-1′-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]-l-threo-biopterin (14) was prepared from l-xylose in an 11-step-sequence. The first synthesis of tepidopterin (3) was achieved by treatment of 14 with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl bromide in the presence of silver triflate and tetramethylurea, followed by removal of the protecting groups.