Ring closure reactionsRing closure reactions O 0130 A Novel and Direct Method for the Preparation of 4-Amino-1,1,3,3-tetrasubstituted Guanidines and of [1,2,4]Triazolo-Fused Heterocyclic Derivatives. -The versatility of the chloroformamidinium salts (II) for the synthesis of guanidine derivatives (III) and of [1,2,4]triazolo-fused heterocycles like (V), (VII), and (IX) is demonstrated. -(ABDUL-GHANI, M.; KHATTAB, S. N.; EL-MASSRY, A. M.; EL-FAHAM*, A.; AMER, A.; Org. Prep. Proced. Int. 36 (2004) 2, 121-127; Dep. Chem., Fac. Sci., Beirut Arab Univ., Beirut, Lebanon; Eng.) -H. Haber 35-033

SummaryThe IR studies for the preactivation step of N-protected iminodiacetic acid with different coupling reagents (TCFH, TFFH, HATU, HBTU, HSTU) were reported here and showed the formation of an anhydride as an active intermediate in case of TCFH and TFFH. The formation of a mixture of an anhydride and an active ester (-OBt, -OAt or -OSu) were observed for HBTU, HATU or HSTU coupling reagent. Dependent on the coupling conditions, acylation of N-protected iminodiacetic acid with amino acid ester or amide derivatives in solution phase gave monoor di-substituted iminodiacetic acid derivatives. Coupling of N-protected iminodiacetic acid with an amino acid or peptide attached to a solid support (PAL-PEG-PS or Wang resin) gave only the monosubstituted iminodiacetic acid derivatives.