Alcoholysis, amino acid derivatives from

Quite remarkable progress has also been achieved in enantioselective transformation of cyclic anhydrides derived from a-hydroxy and a-amino carboxylic acids. By careful choice of the reaction conditions, dynamic kinetic resolution by alcoholysis has become reality for a broad range of substrates. Again, the above mentioned dimeric cinchona alkaloids were the catalysts of choice. In other words, organoca-talytic methods are now available for high-yielding conversion of racemic a-hydroxy and a-amino acids to their enantiomerically pure esters. If desired, the latter esters can be converted back to the parent - but enantiomerically pure - acids by subsequent ester cleavage. 

Derivatives of 5-amino-5-deoxy-L-arabinonic (58) and o-xylonic (59) acids were prepared from the respective per-O-methyl aldono-1,5-lactones (56 and 57). Opening of the lactone by alcoholysis followed by tosylation of... 

---