Synthesis of N-Betsylated Amino Acids Using Aqueous Buffered Sodium Hypochlorite Solution

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Biochemistry

Background:

• Peptide synthesis requires efficient amino acid protection strategies.
• Current methods may suffer from epimerization or limited orthogonality.
• Developing novel protecting groups is crucial for advancing peptide chemistry.

Purpose of the Study:

• To introduce a novel, efficient method for synthesizing N-benzo[d]thiazol-2-sulfonyl (betsyl)-protected amino acids.
• To demonstrate the utility of betsyl-protected amino acids in solid-phase peptide synthesis (SPPS) and solution-phase peptide synthesis.
• To establish the orthogonality of the betsyl protecting group with common protecting groups.

Main Methods:

• In situ generation of benzo[d]thiazol-2-sulfonyl chloride (Bts-Cl) under buffered aqueous oxidative conditions.
• Protection of free amino acids using sodium betsylate.
• Synthesis of a library of betsylated amino acids with diverse side chains.
• Incorporation of N-terminal betsylated residue in a pentapeptide for macrocyclization via Mitsunobu reaction.
• Peptide synthesis using COMU and TCFH/NMI coupling reagents.

Main Results:

• A one-step, epimerization-free synthesis of N-betsyl amino acids was achieved.
• Betsylated amino acids were successfully incorporated into peptides using SPPS and solution-phase methods.
• Macrocyclization was demonstrated using an N-terminal betsylated residue.
• Orthogonal deprotection conditions (basic or reductive) were established for the betsyl group.

Conclusions:

• The new method provides efficient access to betsyl-protected amino acids, valuable building blocks for peptide synthesis.
• Betsyl protection offers versatility for both solid-phase and solution-phase peptide synthesis, including macrocycle preparation.
• The orthogonality of the betsyl group enhances its applicability in complex peptide synthesis strategies.