Starting from chiral-protected 4-hydroxymethyl pyrrolidin-2-ones, the otherwise elusive 3,4-trans-3,3,4-trisubstituted isosteres of α-methyl homoserine, tethered on a γ-lactam ring, were prepared exploiting stereoselective electrophilic aminations. These reactions led to the isolation and characterization of a novel type of atropisomers, exceedingly stable at room temperature, that were directly converted to the desired products by a novel non-reductive N-N bond cleavage reaction.

Electrophilic amination of diastereomeric 4‐methoxycarbonyl pyrrolidin‐2‐ones allowed to prepare both diastereomers of an amino acid bearing a quaternary chiral center, a key intermediate to antibiotic 8‐methoxyquinolone carboxylic acid. Within this synthesis, novel atropisomers, exceedingly stable at room temperature, were isolated and characterized, which were subsequently converted into the desired products by a novel reductive N–N bond cleavage reaction.

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Nα‐acylated β2,3‐3‐azapeptides, or α‐hydrazidopeptides, of different lengths were synthesized starting from a conformationally restricted imidazolidinone‐tethered monomer. The preferential conformations of the oligomers were investigated by NMR and CD spectroscopy, supported by computational analysis. The experimental data clearly confirmed the tendency of these α‐hydrazidopeptides to fold into a zig‐zag (Z8) 8‐helix conformation, whose stability is length‐dependent, stabilized by the C=O(i)···H–N(i + 2) and N(i)···H–N(i + 1) intramolecular H‐bonding pattern, as well as by non‐standard C=O···H‐C hydrogen bonds.

Gabapentin, an antiepileptic drug, is known to form stable helical structures in short peptides. Distinctly, we report on the newly synthesized γ-analogue of gabapentin, that is, γ-gabapentin (γ-Gpn), which manifests β-sheet character at molecular and nanofibrous hydrogels at the supramolecular level. We investigated the influence of proximally immobilized cationic amino acids (lysine and arginine) on the self-assembly of backbone-expanded tripeptide motif. Interestingly, arginine was found to be superior, both physically and mechanically, over lysine in driving hydrogelation. We have concluded that intrinsic and biochemically distinct properties of the guanidinium ion of arginine (compared to ammonium ion of lysine) have contributed towards this effect. Furthermore, similar to pyroglutamyl (pGlu) modified amyloid β peptides, N-pGlu modification of our self-assembling tripeptide motif exerts a dramatic influence on aggregation and exhibits enhanced β-sheet character, accelerated self-assembly kinetics, improved optical transparency and provides higher mechanical stiffness to the peptide hydrogel.