P-hydroxythiolic acid ester

Chiral y-alkoxy-p-hydroxythiolic acid esters CO - C(OH)C — COSR... 

Glycidic from a-bromo-p-hydroxythiolic acid esters... 

A soln. of /er/-butyl bromothioacetate in dichloromethane at —78° treated via syringe with 1.1 eqs. dicyclopentylborinyl triflate in the same solvent followed by 1.2 eqs. of /-Pr2NEt, stirred at —78° for 30 min, a soln. of 2,3-dimethoxybenzaldehyde in dichloromethane added slowly, stirred for a further 2 h at the same temp., 1.2 eqs. /-Pr2NEt added, the mixture warmed to room temp., and stirred for 12 h - / r/-butyl (2R, 3S )-2,3-epoxy-3-(2,3-dimethoxyphenyl)thiopropanoate. Y 62%. This method gives higher /ra 5-selectivity than the classical Darzens glycidic ester condensation. F.e. and isolation of the intermediate a-bromo-P-hydroxythiolic acid esters, also conversion to glycidic acid esters (with Mg(OMe)2) s. R.P. Polniaszek, S.E. Belmont, Synth. Commun. 19, 221-32 (1989). 

Stannous triflate I tri-n-butyltin fluoride j chiral diamine p-Hydroxythiolic acid esters from O-silylketene 0,S-acetals and aldehydes Asym. aldol-type condensation... 

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