Method for producing .alpha.-hydroxy-.beta.-aminocarboxylic acids

A method for producing .alpha.-acyloxy-thioesters of the formula (II):

• ##STR10## wherein R.sup.1 represents an unsubstituted or substituted, linear, branched or cyclic alkanoyl group having from 2 to 18 carbon atoms, an unsubstituted or substituted, linear, branched or cyclic alkoxycarbonyl group having from 2 to 18 carbon atoms, an aralkyloxy carbonyl group having from 7 to 18 carbon atoms, or an unsubstituted or substituted benzyl group, or represents, together with R.sup.2, a residue of a dibasic acid having from 8 to 18 carbon atoms;
• R.sup.2 represents a hydrogen atom or an unsubstituted or substituted benzyl group, or represents, together with R.sup.1, a residue of a dibasic acid having from 8 to 18 carbon atoms;
• R.sup.3 represents an unsubstituted or substituted, linear, branched or cyclic alkyl group having from 1 to 18 carbon atoms, an aralkyl group having from 7 to 18 carbon atoms, or an aryl group having from 6 to 18 carbon atoms;
• R.sup.4 represents an unsubstituted or substituted, linear, branched or cyclic alkanoyl group having from 2 to 18 carbon atoms, or an arylcarbonyl group having from 7 to 18 carbon atoms;
• and
• R.sup.5 represents an alkyl group having 1 or 2 carbon atoms, an aryl group having from 6 to 18 carbon atoms, or an aralkyl group having from 7 to 18 carbon atoms,
• which comprises rearranging, in the presence of a base, an .alpha.-keto-hemimercaptal-carboxylate of the formula (I):
• ##STR11## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 have the same meanings as above.