合成路线1

The vinyl stannane fragment (XI) of the preceding synthesis (scheme 1756502a) is obtained as follows: Treatment of the meso-2,3-dimethylglutaric acid dimethyl ester (XIII) with alpha-chymotrypsin followed by reduction with borane.dimethylsulfide gives the chiral hydroxy ester (XIV), which is protected with BPSCl and the ester group reduced with DIBAL to afford the partially protected diol (XV). The oxidation of (XV) with oxalyl chloride and protection of the resulting aldehyde with propane-1,3-dithiol give the dithiane (XVI), which is deprotected with TBAF and oxidized with oxalyl chloride to yield the aldehyde (XVII). The olefination of (XVII) with methyl iodide and CrCl2 affords the trans-vinyl iodide (XVIII), which is finally treated with butyllithium and tributylstannyl bromide in ethyl ether to give the vinyl stannane fragment (XI).