Enantioselective synthesis of carba-l-furanose precursors of carbanucleosides, using ring-closing metathesis

Carba-l-sugars were synthesized in seven steps from known tetra-O-benzyl-d-galactopyranose (3). The synthesis of cyclopentene ring has been accomplished via a ring-closing metathesis step. Schrockʹs catalyst was employed on the unique diene, key intermediate (5), to provide the cyclopentene derivative (7), a versatile intermediate for the synthesis of carbocyclic nucleosides.