Scheme 2. Route of synthesis of contryphan-Vn disulfide bond mimic; reagents and conditions: (a) (i) N-methyl-N-phenylaniline N-oxide, DCM, rt, 15 min; (ii) TFA/m-cresol/DCM (5 : 20 : 75), v/v/v, rt, 15 min; (iii) 20% piperidine/DMF, rt, 10 min; (iv) PyAOP, HOAt, NMM, NMP, rt, 12 h; (b) TFA/EDT/TIPs/water (95 : 2 : 2 : 1, v/v/v/v), rt, 2 h. The resin-bound peptides were protected on side chains at asterisk sites. The following protecting groups for amino acid side chains were used: tert-butyl (tBu; for Asp) and tert-butyloxycarbonyl (Boc; for Lys and Trp).
