摘要 |
Production of dihydroxycarboxylic acid esters, by reaction of hydroxycarboxylic acid diesters with complex hydrides, is conducted in the absence of a solvent. <??>Production of dihydroxycarboxylic acid esters of formula (I) by reaction of hydroxycarboxylic acid diesters of formula (II) with complex hydrides is conducted in the absence of a solvent. <??>n = 1, 2, 3, 4, 5, 6 or 7; and <??>R<1> and R<2> = optionally substituted 1-20C alkyl, 2-20C alkenyl or alkynyl, 3-8C cycloalkyl, aralkyl, aryl, hetarylalkyl or hetaryl <??>An Independent claim is included for production of R-(+)- alpha -lipoic acid of formula (III) from (I) obtained as above (i.e. in the absence of solvent) by: <??>(1) converting (I) to its bis-sulfonic ester by reaction in an organic solvent with a sulfonic acid chloride and a tertiary nitrogen base; <??>(2) converting the ester thus obtained to R- alpha -lipoic acid ester by reaction in a polar solvent with sulfur and an alkali metal disulfide; and then <??>(3) converting the ester to the required product. |