Stereoselective synthesis of stable isotope labeled L-α-amino acids: synthesis of L-[4-13C] and L-[3,4,-13C2]aspartic acid

We have developed a stereoselective route to isotopically labeled L-aspartic acid using L-serine as a chiral precursor. Labeled serine, prepared biosynthetically was N-protected by conversion to the N-t-Boc derivative. (N-t-Boc)-[3-13C]Serine is cyclized to its β-lactone which was treated with potassium [13C]cyanide to yield L-β-[3,4-13C2]cyanoalanine. Hydrolysis of the cyanoalanine yielded L-[3,4-13C2]aspartic acid. Similarly, L-[4-13C]aspartate was produced from L-serine and K13CN. Using this route, the L-enantiomer was produced in 96% excess. (Author)