[CH2:1]([O:8][C@H:9]([CH3:15])[C@H:10]([OH:14])[C:11](O)=[O:12])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.B(OC)(OC)OC.CSC.B.CO>O1CCCC1>[CH2:1]([O:8][C@H:9]([CH3:15])[C@H:10]([OH:14])[CH2:11][OH:12])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1To a solution of (2S,3R)-3-(benzyloxy)-2-hydroxybutanoic acid (the product of step i) (0.79 g) and trimethyl borate (0.67 mL) in anhydrous tetrahydrofuran (4 mL) at 0° C. was added dropwise borane-dimethyl sulfide complex (3 mL, 2 M in tetrahydrofuran). The reaction mixture was stirred at room temperature overnight, then further borane-dimethyl sulfide complex (3 mL, 2 M in tetrahydrofuran) was added at 0° C. and the reaction mixture stirred at room temperature for a further 2 d. The mixture was cooled to 0° C. and methanol (10 mL) slowly added. When effervescence had ceased, the volatiles were evaporated, further methanol added and the mixture concentrated again to give the subtitle compound as a yellow oil which was used without further purification. Yield: 0.68 g.
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