C(Cl)(=O)C(Cl)=O.CS(C)=O.[CH3:11][C@H:12]([CH2:15][S:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][C:18]=1[O:23][CH3:24])[CH2:13][OH:14].C(N(CC)CC)C>ClCCl>[CH3:11][C@H:12]([CH2:15][S:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][C:18]=1[O:23][CH3:24])[CH:13]=[O:14]0.61 ml (0.007 mol) of oxalyl chloride and 20 ml of dichloromethane are introduced into a round-bottomed flask kept under an inert atmosphere. The mixture is cooled to −78° C. and then 1 ml (0.014 mol) of dimethyl sulfoxide is introduced. After stirring at −78° C. for 15 minutes, 1.5 g (0.007 mol) of 2-(S)-methyl-3-(2-methoxyphenylthio)propan-1-ol (XXb-1), in solution in 15 ml of dichloromethane, are added dropwise. The mixture is stirred at −78° C. for 1 hour and then 2 ml (0.014 mol) of triethylamine are added. After 15 minutes at −78° C., the mixture is reheated to −10° C. and stirred at this temperature for 45 minutes. The aldehyde is not isolated at this stage but is used in situ in the following reductive amination reaction.
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