Practical Synthesis of Methyl Z-2-(N-Acetylamino) but-2-Enoate. An Intermediate to D- and L-2-Aminobutyric Acid

Treatment of inexpensive L- or DL-threonine methyl ester with acetic anhydride and either pyridine or anhydrous sodium acetate at reflux results in dehydration yielding the N,N-diacetamide of the title compound in >80% yield. Monodeacetylation of the diacetamide with 0.1 equiv of triethylamine in methanol affords the title monoacetamido derivative 1 in nearly quantitative yield.