A flexible approach for the synthesis of selectively labelled l-arginine

A simple and efficient synthesis of l-arginine has been achieved in 12 steps and 24% overall yield. Regioselective reduction and functional group manipulation of the β-side chain of aspartic acid allowed the preparation of an ornithine derivative, which was then guanylated with a bis-protected 1-guanyl-pyrazole and deprotected to give l-arginine. This approach allows the flexible incorporation of stable isotopes and this is demonstrated using potassium 13C-cyanide, which has resulted in the preparation of 5-13C-l-arginine.