Fig. 3. In situ construction of dipyrrin derivatives on the peptide YFMVF. Condition: (a) aldehyde-containing carboxylic acid, PyBOP, DIPEA, DMF, 3 h. (b) Pyrrole derivatives, BF3·OEt2, r.t., DMF, overnight; (c) DDQ, 1 h, DCM; (d) TFA/TIPS/H2O, v/v/v, 95/2.5/2.5, r.t., 2 h. aAbsolute Isolated yield compared with the substitution value of the resin–bound peptide. bRelative yield compared with the isolated yield of the unconjugated peptide.c,d No/Very few desired products were detected by LC-MS.
