Efficient introduction of protected guanidines in boc solid phase peptide synthesis.

[reaction: see text] Reaction of primary amines with pyrazole 1 results in rapid and efficient guanidinylation, either in solution or on solid phase. The reaction affords sulfonamide-protected products required for BOC solid phase peptide synthesis (SPPS) in a single step under mild conditions. Incorporation of orthogonally protected side chain amines permits the synthesis of peptides containing arginine analogues, one of which could not be prepared by coupling of preformed amino acids.