Successive addition of N-carboxyanhydride (NCA) Trp to POPC liposomes showed that multiple feeding permits the formation of much longer Trp-oligomers compared to the reference system with no liposomes. Mixed POPC/DDAB liposomes were used to obtain block co-oligopeptides containing both Trp and Glu residues in the same chain. By using the lipophilic condensing agent EEDQ in the absence and presence of POPC liposomes, significant amounts of oligo-Trps were obtained only for the latter case. EEDQ-induced condensation in the presence of POPC liposomes and a library of four dipeptides, H-TrpTrp-OH, H-TrpGly-OH, H-TrpAsp-OH, and H-TrpGlu-OH, led to the selective formation of hydrophobic Trp-oligomers, since H-TrpTrp-OH is the only dipeptide out of the pool that exhibits affinity for the POPC membrane. Oligomers of H-ArgTrp-OH or H-HisTrp-OH were obtained only in significant yields in the presence of negatively charged POPC/DOPA liposomes. The case of the synthesis of H-HisTrpHisTrp-OH is shown as an example of in situ preparation of a reactive, potentially catalytically active compound.