Synthesis of conformationally locked methanocarba-uridine as a precursor for nucleotides agonizing P2Y₆ receptor

Conformationally locked uridine in the 'southern' conformation, which could be an important precursor for corresponding nucleotides, was stereoselectively synthesized. Southern uridine nucleotides are expected to be full agonists for the P2Y₆ receptor. Poor diastereoselectivity in the osmium-mediated dihydroxylation on the allyl amine was overcome by introduction of an allyl azide on which osmium medium hydroxylation, and subsequent cyclization yielded 6-oxabicyclo[3.2.0]heptane in a 9:1 ratio. High regioselectivity between the 2′- and 3′-hydroxyl groups in the intramolecular O-alkylation and construction of uracil moiety from the azido group provided the final target, a southern 2′-benzoylated uridine derivative.