BOP-OXy, BOP-OBt, and BOP-OAt: novel organophosphinic coupling reagents useful for solution and solid-phase peptide synthesis.

Stand-alone coupling reagents derived from bis(2-oxo-3-oxazolidinyl)phosphorodiamidic chloride show efficient performance in solution and SPPS. In particular, the Oxyma Pure (Luxembourg Biotech., Tel Aviv, Israel) derivative shows the additional advantage of being highly soluble in DMF and even fairly soluble in CH3 CN, which can extend its use for the synthesis of complex peptides. These new stand-alone coupling reagents have the advantage of not bearing any counteranion such as PF6 or BH4 , whose presence can jeopardize the purification of final peptides prepared in solution.