Diaminomethane dihydrochloride, a novel reagent for the synthesis of primary amides of amino acids and peptides from active esters

Amide formation from acids, N-protected amino acids and peptides was achieved in an easy and convenient way by treating "active esters" such as succinimidyl or 4-nitrophenyl esters or acyl chlorides with diaminomethane dihydrochloride in dioxane in the presence of Et3N. Diaminomethane dihydrochloride behaves as a slow ammonia-releasing agent. The method is a good alternative to the use of concentrated aqueous ammonia; it avoids solubility problems and allows better control of the stoichiometry of the reaction and of the pH. It gives good yields and does not induce racemization. The mechanism of the reaction is discussed.