合成路线1

Treatment of diketoester (I) with trimethylsilyl diazomethane and diisopropyl ethylamine produced enol ether (II). This was condensed with (S)-2-methyl-4-pentenal (III) in the presence of LDA at -120 C to afford the aldol condensation product (IV) as the major isomer. Protection of the 7-hydroxyl group of (IV) with trichloroethoxycarbonyl chloride gave carbonate (V). Enol ether of (V) was then hydrolyzed with p-TsOH in acetone to provide diketoester (VI). Hydroboration of the terminal olefin of (VI) with 9-borabicyclo[3.3.1]nonane gave organoborane (VII). Then, Suzuki coupling of (VII) with vinyl iodide (VIII), followed by acid hydrolysis of the silyl protecting group, provided the thiazolyl heptadecadienoate (IX). Asymmetric hydrogenation of 3-keto group of (IX) in the presence of the modified Noyori's catalyst [RuCl2(R)-BINAP)]2[Et3N] furnished the desired 3-(S) alcohol (X).

合成路线2

The treatment of diketoester (XII) with trimethylsilyl diazomethane and DIEA gives enol ether (XIII), which is condensed with 2(S)-methyl-4-pentenal (XIV) by means of LDA to yield the aldol condensation product (XV) as the major isomer. The protection of the OH group of (XV) with Troc-Cl and pyridine affords the trichloroethyl carbonate (XVI), whose enol ether group is hydrolyzed with TsOH in acetone to provide the diketoester (XVII). The condensation of (XVII) with iodovinyl intermediate (XI) by means of BBN, (dppf)2PdCl2, AsPh3 and Cs2CO3 in THF/DMF/water gives adduct (XVIII), which is desilylated by means of HCl in methanol to yield the secondary alcohol (XIX). The asymmetric hydrogenation of (XIX) with H2 over a chiral Ru catalyst in acidic methanol affords the secondary diol (XX), which is silylated with Tes-OTf and lutidine to provide the bis-silyl ether (XXI). The selective desilylation of (XXI) with simultaneous hydrolysis of its tert-butyl ester by means of HCl in methanol gives the hydroxyacid (XXII) suitable for cyclization.

合成路线3