Synthesis of tritiated poly‐L‐lysine (γ, δ‐T₂)

Tritiated poly‐ L ‐lysine (γ, δ‐T 2 ) (IX) was prepared according to the following procedure: Tritiated DL ‐lysine (γ, δ‐T 2 ) (III) was derived from acetamino‐(‐4‐amino‐Δ 2 ‐butenyl)‐diethylmalonate (I) by tritiation followed by acid hydrolysis. The racemic tritiated lysine was converted to its ε, N ‐trifluoroacetyl derivative IV, and the latter resolved via its chloroacetyl derivative by means of hog kidney acylase. The optically active tritiated ε, N ‐trifluoroacetyl‐ L ‐lysine (VI) was converted into the corresponding N ‐carboxyanhydride VII with phosgene, and polymerization carried out in dioxane using triethylamine as initiator. The required tritiated poly‐ L ‐lysine (IX, n = 250) was obtained from the blocked polymer VIII after removal of the protecting groups with piperidine. The tritiated polypeptide possessed an activity of 250 mC. per mmole lysine residue. The procedure described enables, however, the preparation of poly‐ L ‐lysine with up to 25 times higher specific activity.