合成路线1

The enantioselective condensation of 3-(trimethylsilyl)propynal (V) with allylmagnesium bromide (VI) by means of (+)-Ipc2B-OMe as chiral catalyst gives hex-5-en-1-yn-3(R)-ol (VII), which is silylated with Tbdps-Cl and imidazole to yield the silyl ether (VIII). The oxidation of the terminal double bond of (VII) by means of OsO4 and NaIO4 affords the aldehyde (IX), which is submitted to a Wittig condensation with the phosphorane (X) in benzene to provide the unsaturated ester (XI). The enantioselective dihydroxylation of the double bond of (XI) with AD-mix-beta in tert-butanol/water gives the dihydroxyester (XII), which is protected with 2-methoxypropene (XIII) and PPTS to yield the isopropylidene ketal (XIV). The bromination of the triple bond of (XIV), followed by selective hydrogenation, affords the cis-bromovinyl compound (XV), whose ester group is reduced with LiAlH4 in THF to provide the primary alcohol (XVI). The oxidation of (XVI) with (COCl)2 and TEA in DMSO gives the carbaldehyde (XVII), which is submitted to a Wittig condensation with the phosphorane (XVIII) in hot dichloromethane to yield the diunsaturated aldehyde (XIX). The enantioselective condensation of aldehyde (XIX) with allylmagnesium bromide catalyzed by (+)Ipc2-B-OMe affords the chiral alcohol (XX), which is esterified with acryloyl chloride (XXI) and DIEA in dichloromethane to provide the ester (XXII). Compound (XXII) is submitted to a ring-closing metathesis catalyzed by a Rh catalyst (Grubbs's catalyst), yielding the dihydropyran derivative (XXIII), which is submitted to cleavage of the acetonide group by means of Montmorillonite K 10 to afford the diol (XXIV). The condensation of the bromovinyl group of (XXIV) with the intermediate boronic ester (IV) by means of Pd(PPh3)4 and Ag2O gives compound (XXV) with the complete backbone of the target fostriecin. The selective monosilylation of (XXV) with Tbdps-OTf gives the intermediate (XXVI).