Synthesis of 3-methylpseudouridine and 2'-deoxy-3-methyl-pseudouridine.

The first chemical synthesis of 3-methyl-psi-uridine (5) and its 2'-deoxy analogue (9) has been achieved. psi-Uridine was trimethylsilylated and the crude product was treated with acetyl chloride, to give the 1-acetyl derivative (3). Crude 3 was methylated with dimethoxymethyldimethylamine and then saponified, to give crystalline 5 in 82% overall yield. Treatment of 5 with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane afforded the 3'5'-protected product, which was converted into the 2'O-[(imidazol-1-yl) thiocarbonyl] derivative 7. Reduction of 7 with tributyltin hydride followed by deblocking of the product gave crystalline 2'-deoxy-3-methyl-psi-uridine (9) in 35% yield form 5.