合成路线1

Synthesis of the intermediate butyraldehyde (X): The Sharpless asymmetric epoxidation of 2(E)-buten-1-ol by means of t-Bu-OOH and D-(-9-diisopropyl tartrate gives the epoxy alcohol (II), which is treated with Tbdps-Cl, TEA and DMAP to yield the silyl ether (III) The condensation of (III) with 1,3-dithiane (IV) by means of BuLi in THF/HMPA affords the cyclic thioketal (V), which is deprotected by means of TBAF in THF, affording the diol (VI). The reaction of (VI) with 4-methoxybenzaldehyde dimethylacetal (VII) by means of TsOH in DMF provides the benzylidene ketal (VIII), which is submitted to a selective opening by means of DIBAL in dichloromethane to give the secondary benzyl ether (IX). Finally this compound is oxidized with SO3/Pyridine and TEA in DMSO/dichloromethane to obtain the target intermediate, the chiral butyraldehyde (X).