A COMPARATIVE-STUDY OF BOP AS A COUPLING AGENT USING SIMULTANEOUS MULTIPLE PEPTIDE-SYNTHESIS

A parallel simultaneous synthesis of multiple peptide was carried out in which the coupling agents BOP and DIPCI were compared. For peptides lacking Asn, no differences in average yield or RP HPLC purity were f ound. For peptides having Asn in their sequences, however, the yield a nd purity were significantly lower for BOP when compared to DIPCI. The addition of HOBt to BOP mediated couplings did not lead to improved r esults. In fact. BOP condensations without HOBt gave, on average, slig htly purer peptides. Comparing the results for peptides prepared with BOP dissolved in DMF, NMP, or NMP + 20% DMSO, NMP afforded the best an d DMF the worst results, but the differences were not significant. Pep tides prepared using BOP, combined with in situ neutralization, were o btained both in higher yield and purity when compared with classical n eutralization. In all BOP mediated couplings, peptides with Asn were o btained in lower yield and purity than peptides without Asn. FAB MS an d amino acid analysis revealed that the side products are peptides wit h deleted Asn.