4-Oxa(thia)-9-oxa-2-azabicyclo[4.2.1]nonane-3-on(thion) derivatives

The synthesis of 7,8-dihydroxy-2-(2-methoxycarbonylethyl)-4,9-dioxa-2-azabicyclo[4.2.1]nonane- 3-thione ( 16 ) and of its parents 9-oxa-4-thia-3-thione 17 , and 9-oxa-4-thia-3-one 18 is described. The conversion of 5′-deoxy-5′-iodo-2′,3′-O, O-isopropylidene-5,6-dihydrouridin ( 1 ) into the 2-O-methyl-5,6-dihydrouridine 5 , the 5′-O-acetyl-5,6-dihydrouridine 4 , and into the N-(5-O-acetyl-2,3-O, O-isopropylidene-β-D -ribofuranosyl)-N-(2-methoxycarbonyl thyl)-urea ( 6 ) invoked 2′,3′-O, O-isopropylidene-2,5′-anhydro-5,6-dihydrouridine ( 2 ) as the common intermediate.