Solid-phase synthesis of N-acyl-N′-carbamoylguanidines

Amino acids immobilized on polystyrene-Wang or Rink amide resin were reacted with p-nitrophenyl chloroformate to give an activated urethane that was displaced by S-methylisothiourea. Following N-acylation with an acid chloride, the thiomethyl group was displaced by primary or secondary amines with the aid of mercury (II) chloride to yield the unsymmetrically substituted title compounds after resin cleavage.