合成路线1

Synthesis of the chiral 5-oxopentanoic ester intermediate (XI): The reaction of 3-hydroxy-2(S)-methylpentanoic acid methyl ester (I) with 4-methoxybenzyl trichloroacetimidate gives the aryl ether (II), which is treated with ethylmagnesium bromide to yield the ketone (III). The condensation of (III) with formaldehyde by means of (c-Hex)2B-Cl and H2O2 affords the hydroxypentanone (IV), which is reduced by means of NaBH(OAc)3 in THF/AcOH to provide the diol (V). The regioselective oxidation of the primary alcohol of (V) with TEMPO and BAIB in dichloromethane gives the beta-hydroxyaldehyde (VI), which is further oxidized with NaClO2 yielding the carboxylic acid (VII). The esterification of (VII) by means of Me-I and K2CO3, or with TMS-CHN2 affords the methyl ester (VIII), which is treated with Tbdms-OTf and lutidine to provide the silyl ether (IX). The selective deprotection of (IX) by means of DDQ in dichloromethane furnishes the omega-hydroxyester (X), which is finally submitted to a Swern oxidation to yield the chiral 5-oxopentanoic ester intermediate (XI).