D-histidine is difficult to extract in large quantities from natural products, and is often prepared by configurational conversion of L-histidine. L-histidine undergoes an asymmetric conversion reaction catalyzed by salicylaldehyde using (R)-tartaric acid as a resolving agent and acetic acid as a solvent to yield D-histidine·(R)-tartrate (yield 98.69%, optical purity 98.26%). The process conditions are: reactant molar ratio: L-histidine:(R)-tartaric acid:salicylaldehyde = 1:1:0.05, reaction temperature 90℃, and reaction time 4 h. D-histidine·(R)-tartrate is then treated in methanol with 2 mol/L triethylamine to obtain D-histidine, with a yield of 94.06% and optical purity of 98.70%. The overall yield of D-histidine is 92.87%. The target compound N-Fmoc-N'-trityl-D-histidine is then prepared by Fmoc protection and Grignard reagent.
