PyBOP

PyBOP is an efficient coupling reagent utilized in solid phase peptide synthesis.  It has reactivity similar to BOP, but its byproduct is not highly carcinogenic. PyBOP was utilized in the solid-phase synthesis of the tetrapeptide H-Ile-Ala-Leu-Pro-OH on 2-chlorotrityl resin.  HPLC analysis of the final peptide showed a single peak (API Conference Proceedings, 1848, 030006 (2017)). in contrast to uronium-based coupling reagents, PyBOP does not form guanidinated byproducts when used in excess. This makes it useful in fragment condensation reactions and head-to-tail cyclizations.