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Repetitive BOP coupling (REBOP) in solid phase peptide synthesis. Luliberin synthesis as model
1CNRS-INSERM, Center of Pharmacology-Endocrinology, Montpellier, France.
International Journal of Peptide and Protein Research
|May 1, 1990
Summary
This study demonstrates the effectiveness of the BOP reagent in synthesizing luliberin (LH-RH) and its D-derivative using protected amino acids. The research highlights efficient methods for peptide synthesis and purification, minimizing racemization.
Area of Science:
- Organic Chemistry
- Medicinal Chemistry
- Biochemistry
Background:
- Luliberin (LH-RH) is a decapeptide hormone with significant physiological roles.
- Efficient and cost-effective synthesis of LH-RH and its analogs is crucial for research and therapeutic applications.
- Classical protection strategies for amino acids can present challenges in peptide synthesis, particularly regarding racemization.
Purpose of the Study:
- To evaluate the efficacy of (benzotriazol-1-yloxy)tris-(dimethylamino)phosphonium (BOP) hexafluorophosphate as a coupling reagent for LH-RH synthesis.
- To investigate the use of inexpensive, classically protected Boc-amino acids in solid-phase peptide synthesis.
- To compare the synthesized LH-RH with its [D-His2] analog using spectroscopic methods and assess purification strategies.
Main Methods:
- Solid-phase peptide synthesis utilizing benzhydryl amino resin and Boc-protected amino acids.
- Employing BOP hexafluorophosphate as the coupling reagent without additional additives.
- Characterization of synthesized peptides using proton nuclear magnetic resonance (1H NMR) spectroscopy.
- Analysis of purity and racemization via high-performance liquid chromatography (HPLC).
Main Results:
- BOP hexafluorophosphate facilitated the synthesis of LH-RH with good solubility of the reagent and by-products, suitable for automated synthesis.
- Unprotected pyroGlu and Boc-His allowed for synthesis with minimal racemization, but Boc-His(Boc) proved superior, yielding no detectable racemization or by-products.
- Biological tests and HPLC confirmed the purity and integrity of the synthesized peptides.
- A recycling procedure in reversed-phase HPLC successfully isolated the minor D-derivative from the LH-RH preparation.
Conclusions:
- BOP hexafluorophosphate is an effective coupling reagent for synthesizing LH-RH using cost-effective Boc-amino acids.
- The use of Boc-His(Boc) is recommended to prevent racemization during LH-RH synthesis.
- Recycling reversed-phase HPLC is a viable strategy for isolating difficult-to-separate peptide isomers.