Solid-phase fragment condensation for synthesis of peptides from the immunodominant sequence of β1-adrenoreceptor

The P26 peptide corresponding to the 197–222 sequence of the second extracellular loop of the β1-adrenoreceptor (β1-AR) was synthesized by solid-phase fragment condensation on the Wang polymer. Pentapeptide fragments were prepared on the 2-chlorotrityl resin. The racemization degree of the C-terminal alanine residue of the pentapeptide was experimentally evaluated for the synthetic H-Glu-Ser-Asp-Glu-Ala-Arg-OH hexapeptide β1-АR-(202–207) which was prepared by the 5 + 1 fragment condensation with the use of various condensing agents. A content of the diastereoisomeric peptide in the products of the fragment condensation was determined by HPLC on a reversed phase. The D-alanine-containing hexapeptide was specially synthesized and used for a comparison. The minimum racemization degree of the C-terminal alanine residue was observed if complex F was applied to the synthesis of the hexapeptide.