Tartaric Acid Amides by the Gabriel Route

Optically active (3 R ,4 R )‐3,4‐diacetoxypyrrolidine‐2,5‐dione was prepared from L ‐tartaric acid by ring closure of the ammonium salt of (2 R ,3 R )‐2,3‐diacetoxy‐3‐carbamoylpropanoic acid with thionyl chloride. Mechanistic considerations indicate that the ring closure proceeds through two competing pathways: either direct ring closure of an intermediate acyl chloride or in a parallel route via a ketene intermediate. The cyclic product was further converted into the optically active tartramonoamides and tartradiamides by hydrolysis and reaction with appropriate alkylamines, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)