Solution-phase-peptide synthesis without purification of column chromatography and recrystallization by protecting amino acid esters with phosphinyl chloride

Biphenyl phosphinyl chloride (Bpp-Cl) has been successfully applied for the amino acid GAP (Group-Assisted Purification) protection. The resulting N-protected amino acid esters have been readily converted into the corresponding amino acids and peptides through GAP operation. Biphalin, enkephalin derivatives and the fragments of surfaxin have also been synthesized via GAP work-up by avoiding column chromatography. The GAP protecting group (Bpp) can be recovered and can implement the former phosphonyl groups in peptide synthesis.