Synthesis of the enantiomeric 2‐pyrrolidineacetic acids.Starting from the enantiomeric Z‐prolines (1) the title compounds9were prepared in optically pure form by using theArndt‐Eistertprocess. It could be shown by chemical correlation that the stereochemical determining step of the reaction sequence, theWolffrearrangement of the N‐acylated diazomethyl ketones5, proceeds with strict retention of configuration. Some known chiroptical methods for determination of absolute configuration were applied to the target co