How is N~6~-(Trifluoroacetyl)-L-lysyl-L-proline (CAS: 103300-89-6) typically synthesized?

N~6~-(Trifluoroacetyl)-L-lysyl-L-proline is synthesized via a multi-step process involving the coupling of L-lysine and L-proline with trifluoroacetyl chloride in the presence of a catalyst such as 1-hydroxybenzotriazole (HOBt). The reaction is typically performed in an inert solvent like dichloromethane, followed by purification steps such as recrystallization or column chromatography to obtain the desired product with high yield and selectivity.