合成路线1

The condensation of benzylated D-arabinofuranose (I) with phosphonate (II) in benzene gives the unsaturated ester (III), which is reduced with DIBAL in dichloromethane, yielding the alcohol (IV). The selective monosilylation of (IV) with Tbdms-Cl, TEA and DMAP in DMF affords the silyl ether (V), which is treated with chloromethylsulfonyl chloride and pyridine to provide the sulfonate (VI). The reaction of (VI) with CsOAc and a crown ether in toluene gives the acetate (VII) with inversion of the configuration at the acetoxy group. Hydrolysis of the acetate group with NaOMe in THF yields the alcohol (VIII), which is chloromesylated as before, affording the sulfonate (IX). The treatment of (IX) with HCl in THF eliminates the silyl group, providing the unsaturated alcohol (X), which is epoxidized with tBu-OOH, Ti(OAc)4 and D-(-)-diethyl tartrate to give the chiral epoxide (XI). The reaction of (XI) with sodium azide in DMF yields the azido compound (XII) with the correct steric configuration. The reductive cyclization of (XII) with PPh3, H2 and Pd/C in methanol affords the pyrrolidine (XIII), which is N-protected with Boc2O and TEA in dichloromethane, providing the carbamate (XIV). Oxidative cleavage of the vicinal diol of (XIV) with Pb(OAc)4 in toluene gives the carbaldehyde (XV).