Synthesis of the 5′-Fluoro-2′β-methyl analogues of neplanocin

Synthesis of the 5′-fluoro-2′-β-methyl analogues of neplanocin was carried out. Key intermediate cyclopentenone 19 was prepared from methyl α-D-mannopyranoside by a new approach consisting of ring-closing metathesis, stereoselective introduction of the 2′-methyl group, and intramolecular oxyselenenylation of the double bond as representative steps. Subsequent introduction of a fluorine atom at the 5′-position of 19 was performed by electrophilic fluorination by using Selectfluor Synthesis of 5′-fluoro-2′β-methyl analogues of neplanocin is described. The common carbocyclic unit was prepared from methyl α-D-mannopyranoside by ring-closing metathesis, stereoselective introduction of a methyl group, intramolecular oxyselenation, and electrophilic fluorination as representative steps.