合成路线1

The intermediate (S)-3-(2-mesyloxyethoxy)-4-(triphenylmethoxy)-1-butanol mesylate (VIII) has been obtained as follows: The hetero Diels Alder cyclization of ethyl glyoxylate (I) with butadiene (II) in toluene at 160-70 C gives racemic 3,6-dihydro-2H pyran-2-carboxylic acid ethyl ester (III), which is submitted to enzymatic resolution by means of B.lentus protease, yielding a mixture of the hydrolyzed (R)-acid and unchanged (S)-ester (IV), that is easily separated. The reduction of the (S)-ester (IV) by means of LiAlH4 in THF affords the hydroxymethyl derivative (V), which is treated with Tr-Cl and DMAP in pyridine to provide the trityl ether (VI). Ozonolysis of the dihydropyran ring of (VI) by means of ozone and NaBH4 in dichloromethane/methanol gives (S)-3-(2-hydroxyethoxy)-4-(triphenylmethoxy)-1-butanol (VII). Finally this compound is treated with Ms-Cl and TEA in dichloromethane to yield the target intermediate (S)-3-(2-mesyloxyethoxy)-4-(triphenylmethoxy)-1-butanol mesylate (VIII). (see scheme no. 25239601a, intermediate no. (X).