合成路线1

The reaction of allyl alcohol (I) with triethyl orthoacetate at 120 C gives the 4-pentenoic ester (II), which is hydrolyzed with KOH to the corresponding free acid (III). The reaction of (III) with (COCl)2 yields the acyl chloride (IV), which is condensed with 4(S)-isopropyloxazolidin-2-one (V) (a chiral auxiliary), by means of BuLi to afford the chiral imide (VI). The diastereoselective alkylation of (VI) with benzyloxymethyl chloride (VII) by means of TiCl4 and TEA in dichloromethane provides the alkylated compound (VIII) with a diastereoselectivity of 70/30% and combined yields of 84%. The reductive elimination of the chiral auxiliary in (VIII) by means of LiAlH4 gives the alcohol (IX), which is treated with Ac2O to yield the acetate (X). The cyclization of (X) by means of I2 and pyridine in acetonitrile affords the chiral tetrahydrofuran (XI)????XI)a, which is condensed with the sodium salt of 1,2,4-triazole (XII) in hot DMF to provide the adduct (XIII). The debenzylation of (XIII) with H2 over Pd/C gives the alcohol (XIV), which is finally treated with Ts-Cl and pyridine to give rise to the target intermediate tosylate (XV) (see scheme no. 20027601a, intermediate no. (II))