Synthesis and Conformational Analysis of Optically Active Poly(#beta#-peptides)

摘要

Optically active poly(#beta#-peptides) with proteinogenic side chains were synthesized via the polymerization of #beta#-amino acid-N-carboxyanhydrides(#beta#-NCAs) initiated using either NaOtBu or a nickel amido amidate complex.Although most of these low molecular weight poly(#beta#-peptides) have poor solubility in common organic solvents,those that were soluble were found to adopt a helical conformation in solution.Poly(N_(#xi#)-carbobenzyloxy-#beta#-L-homolysine) (2f) was observed to adopt a helical conformation in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP),which could be disrupted by addition of methanesulfonic acid (MSA),a strong denaturing agent.The side-chain deprotected polymers,poly(#beta#-L-homolysine) (3) and poly(#beta#-L-homoglutamate) (4),were found to display pH-dependent conformation transitions in aqueous solution.