D. Bonnet F. Samson C. Rommens H. Gras-Masse O. Melnyk Authors' af®liations: D. Bonnet, F. Samson, C. Rommens, H. Gras- Masse and O. Melnyk, Institut Pasteur de Lille/ Institut de Biologie de Lille and Universite  de Lille 2, 1 rue du Professeur Calmette 59019 Lille, France. Correspondence to: Oleg Melnyk Institut Pasteur de Lille/Institut de Biologie de Lille et CNRS 1 rue du Professeur Calmette 59019 Lille France Tel: 3-2087-1215 Fax: 3-2087-1233 E-mail: oleg.melnyk@pasteur-lille.fr Dates: Received 20 October 1998 Revised 4 December 1998 Accepted 16 February 1999 To cite this article: Bonnet, D., Samson, F., Rommens, C., Gras-Masse, H. & Melnyk, O. Synthesis of hydrazinopeptides using solid- phase N-electrophilic amination: extension to the Fmoc/ tert-butyl strategy and chemistry on the N±N bond in strong acid media. J. Peptide Res., 1999, 54, 270±278. Copyright Munksgaard International Publishers Ltd, 1999 ISSN 1397±002X Synthesis of hydrazinopeptides using solid-phase N-electrophilic amination: extension to the Fmoc/tert-butyl strategy and chemistry of the N±N bond in strong acid media Key words: cleavage step; dianisylpeptides; Hofmann-type elimination; hydrazinopeptides; N-electrophilic amination; solid- phase synthesis Abstract: The synthesis of hydrazinopeptides using solid-phase N-electrophilic amination was extended to the Fmoc/tert-butyl strategy. Both Boc/benzyl and Fmoc/tert-butyl strategies led to the isolation of by-products arising from the partial instability of the N±N bond during the ®nal cleavage and deprotection step. Two paths of decomposition have been shown: the cleavage of the N±N bond leading to the regeneration of the amine and a Hofmann-type elimination yielding original dianisyl adducts. Our data suggest that the Fmoc/tert-butyl strategy is better suited for the synthesis of hydrazinopeptides. Abbreviations: 2-BrZ, 2-bromobenzyloxycarbonyl; 2-ClZ, 2-chlorobenzyloxycarbonyl; BCPO, N-Boc-3- (4-cyanophenyl)oxaziridine; Boc, tert-butyloxycarbonyl; Bzl, benzyl; cHex, cyclohexyl; CZE, capillary zone electrophoresis; DIEA, diisopropylethylamine; DMF, dimethylformamide; DMSO, dimethylsulfoxide; Dnp, dinitrophenyl; ES-MS, electrospray mass spectrometry; Fmoc, 9-¯uorenylmethoxycarbonyl; HBTU, N-[(1H- benzotriazol-1-yl)(dimethylamino)methylene]-N- methylmethanaminium hexa¯uorophosphate N-oxide; HF, hydro¯uoric acid; HOBt, N-hydroxybenzotriazole; MBHA, 4-methyl benzhydrylamine resin; Mtt, 4-methyltrityl; Palm, palmitoyl; PDMS, plasma desorption mass spectrometry; Pmc, 2,2,5,7,8-pentamethylchroman-6-sulphonyl; Rink amide resin, 4-(2',4'-dimethoxyphenyl-Fmoc-aminomethyl)-phenoxy resin; tBu, tert-butyl; TFA, tri¯uoroacetic acid; TOF, time-of-¯ight; Tos, tosyl; Trt, trityl. 270