We developed a one-pot synthetic technique for alternating peptides. Central to this technique is a new, catalyst-free polymerization based on Ugi's 4CC reaction. The treatment of imines with the ambident molecules bearing both an isocyanide and a carboxylic acid afforded alternating peptides.

Elastin-like polypeptides containing proline were synthesized via chemoenzymatic polymerization and exhibited a temperature-dependent structural transition.

Polypeptides containing periodic aromatic residues in their main chains were synthesized via papain-catalyzed chemoenzymatic polymerization of tripeptide ester monomers under moderate conditions in aqueous buffers. As the monomer, 4-aminobenzoic acid (Abz) was modified with Gly or Ala at the N-and C-termini to mitigate the poor substrate specificity of papain to unnatural amino acids. The tripeptide esters, namely, GlyAbzGly and AlaAbzAla ethyl esters, can be recognized and polymerized by papain, resulting in the polypeptides poly(GlyAbzGly) and poly(AlaAbzAla), respectively, with periodic sequences containing Abz units every three residues. Copolymerization of tripeptide esters with Gly or Ala ethyl ester also proceeded in the presence of papain. The secondary structures of the Abz-containing polypeptides were investigated by IR and wide-angle X-ray diffraction (WAXD) analysis. The WAXD profile of poly(GlyAbzGly) was similar to that of polyGly, whereas poly(AlaAbzAla) adopted a sheet-like structure similar to the β-sheet of polyAla. Thermal analysis of Abz-containing polypeptides revealed that the high thermal stability of the Abz-containing polypeptides is related to the distinct sequences that periodically include Abz residues.

R)-1,1′-Bi(2-naphthol) was reacted with 1,4-phenylene diisocyanate leading to a mixture of linear polyurethane and cyclic compounds including a cyclic dimer and a cyclic trimer. The structure of the cyclic dimer was elucidated by X-ray crystal structure analysis. The polymer was proposed to possess a rather stiff, π-stacked, 2/1-helical conformation on the basis of NMR, CD, and UV spectra and molecular dynamics simulations. The conformation was stable in the range of temperature of 0−60°C. U rethane bond is readily formed through a reaction between alcohol and isocyanate even without a catalyst, and a reaction between diol and diisocyanate leads to polyurethane. Polyurethane is an important class of polymer which can be applied for a wide variety of chemical products, including various types of foams, elastomers, fibers, coatings, and adhesives. 1 Further, aiming at more advanced functions, chiral polyurethanes have been prepared 2 since chirality plays an important role in attaining useful polymer properties. 3 Herein we report the synthesis of a chiral polyurethane from optically active (R)-1,1′-bi(2-naphthol) (R-BINOL) and 1,4-phenylene diisocyanate (PDI). Binaphthyl is one of the most effective chiral organic groups in inducing a specific structure to a polymer, and a series of binaphthyl-based polymers were prepared and found to exhibit various functions, such as catalysis and light emission. 4 Although a BINOL-PDI reaction product was once reported, 5 its structure and reaction details have never been examined. This work focuses on the two aspects of the synthesis, that is, (i) chain topology (cyclic or linear) and (ii) chain conformation. As for chain topology, in general, a cyclic chain can form in addition to a linear chain in polyaddition or polycondensation. Formation of cyclic compounds has been explored for polyamides 6 and polylactones, 7 but not for a chiral polyurethane system. We found that both cyclic and linear chains are produced where their ratio can be controlled by tuning reaction conditions. As for chain conformation, a π-stacked, 2/1-helical conformation is proposed for the linear polymer. Such a conformation has been known only for limited polymers, including syndiotactic polystyrene and poly(p-methylstyrene) and some polydienes in the solid state. 8Reactions between R-BINOL and PDI were conducted in tetrahydrofuran (THF) in the presence of triethylamine (TEA) at a reagent concentration, [BINOL] = [PDI] = 0.031, 0.154, or 0.931 M and [TEA] = 0.48 M, at a temperature of 0, 23, or 60°C for reaction durations from 5 s to 24 h (Scheme 1). The reactions were terminated by adding MeOH or by exposure to air. In all reactions examined in this study except for those for 3 min or shorter time, the monomers were almost completely consumed. The reaction products were found to include linear poly(BINOL-PDI), as well as oligomeric species, such as 1−3, indicated in Scheme 1. Figure 1 shows the SEC curves of the polymerization products obtained by changing reagent concentration (A), temperature (B), ...

A facile approach to synthesize nature‐mimetic polypeptides via the formation of N‐protected intermediates is developed. The approach is based on the use of stable and easily cleavable N‐(1‐p‐methoxyphenethyl) (MPE) group as a new N‐protecting group for an amide group. The MPE‐protected polypeptides are prepared in one‐pot via three‐component polycondensation using amino acid–free starting materials. Subsequent acidic treatment of the obtained polypeptides result in the perfect removal of MPE to give the nature‐mimetic polypeptides consisting of alternating peptide skeleton. The aqueous solutions of the nature‐mimetic polypeptides exhibit thermal responsivity depending on the structure of pendant functionalities.