合成路线1

2) The intermediate 3(R)-(p-toluenesulfonyloxy)thiolane (VII) can be obtained by two other synthetic pathways: a) The racemic 2-hydroxy-4-(methylsulfanyl)butyric acid ethyl ester (XVIII) is submitted to optical resolution with Pseudomonas fluorescens lipase in toluene/water, yielding the corresponding 2(R)-hydroxy ester (XIX), which is reduced with NaBH4 in THF/water to afford 4-(methylsulfanyl)butane-1,2(R)-diol (XX). The acylation of (XX) with p-toluenesulfonyl chloride and pyridine yields the ditosylate (XXI), which is cyclized in refluxing benzene to give 1(R)-methyl-3(R)-(p-toluenesulfonyloxy)thiolanium p-toluenesulfonate (XXII). Finally, this compound is treated with trifluoroacetic acid in pyridine to afford the thiolane (VII), already described. b) The reduction of 4-chloro-3(R)-hydroxybutyric acid methyl ester (XXIII) with lithium borohydride in THF gives 4-chlorobutane-1,3(R)-diol (XXIV), which is tosylated as before, yielding the bis(tosyloxy) derivative (XXV). Finally, this compound is cyclized with Na2S in hot acetonitrile/water to afford the thiolane (VII), already described.