SYNTHESIS OF AN N-3-GUANIDINOPROPYLGLYCINE (NARG) DERIVATIVE AS A VERSATILE BUILDING-BLOCK FOR SOLID-PHASE PEPTIDE AND PEPTOID SYNTHESIS

N-(2, 2, 5, 7, 9-fluorenylmethoxycarbonylglycinyl)propylguanidine (1) was prepared and utilized as an arginine surrogate (Narg) building blo ck compatible with solid-phase synthesis according to the Fmoc methodo logy. Narg is potentially useful in the assembly of combinatorial comp ound libraries or in the preparation of modified peptides. The applica bility of this building block was demonstrated by its incorporation in to an analogue of Thr-Arg-Ser-Ala-Trp, a pentapeptide for which inhibi tion of osteoclastic bone resorption was claimed. The modified pentape ptide showed an increased proteolytic stability when compared to the o riginal inhibitor.