Synthesis of enantiomerically pure α-hydroxyaldehydes from the corresponding α-hydroxycarboxylic acids: novel substrates for Escherichia coli transketolase

Enantiomerically pure (R)-α-hydroxyaldehydes (>95% ee) are prepared from the corresponding α-hydroxyesters by silyl protection, reduction with diisobutylaluminium hydride, and finally deprotection under acidic conditions; subsequent coupling of these aldehydes with lithium hydroxypyruvate, catalysed by Escherichia coli transketolase, leads to novel optically pure triols.