A synthesis of pseudouridine and of 5-β- D -ribofuranosyluridine

5-Bromo-2,4-di-t-butoxypyrimidine is converted into the pyrimidin-5-yl-lithium and coupled to 2,4:3,5-di-O-benzylideneribose. Mild acid treatment of the intermediate protected 1-pyrimidin-5-ylpentitol affords 5-β-D-ribofuranosyluracil, pseudouridine, with some α-anomer and only traces of the pyranose isomers. Likewise 5-bromo-2′,3′-O-isopropylideneuridine leads to 5-β-D-ribofuranosyluridine (1,5-diribosyluracil).