Unnatural Amino Acid: 4-Aminopyrazolonyl Amino Acid Comprising Tri-Peptides Forms Organogel With Co-Solvent (EtOAc:Hexane)

Ampyrone is an amino-functionalized heterocyclic pyrazolone derivative that possesses therapeutic values such as analgesic, anti-inflammatory, and antipyretics. The chemical structure of ampyrone exhibits excellent hydrogen bonding sites and is considered as the potential scaffold of supramolecular self-assembly. Recently, this molecule has been derived into unnatural amino acids such as aminopyrazolone amino acid and its peptides. This report describes that one of its amino acids, O-alkylated ampyrone, containing hybrid (α/β) peptides forms organogel after sonication at 50–55°C with 0.7–0.9% (w/v) in ethyl acetate: hexane (1:3). The formation/morphology of such organogels is studied by nuclear magnetic resonance Fourier-transform infrared (FT-IR), circular dichroism (CD), scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (Powder-XRD), and thermogravimetric analysis (TGA). Energy-minimized conformation of APA-peptides reveals the possibility of intermolecular hydrogen bonding. Hence, APA-peptides are promising peptidomimetics for the organogel-peptides.

Effect of C12H25O– substituent position on the self-assembly behaviour of C6H5COO–Ala–Ala dipeptide

Intramolecular hydrogen bonding and steric hindrance of side chain lead the different molecular packing of dipeptides and the morphological transformation of self-assemblies’ nanostructures.

Cleavable Amide Bond: Mechanistic Insight into Cleavable 4-Aminopyrazolyloxy Acetamide at Low pH

The cleavage of amide bonds under mild acidic conditions is a rare chemical event. N-Acetamide bond of peptides is extremely stable even under the strongest organic acid trifluoromethanesulfonic acid. This report mechanistically describes a new cleavable amide bond in 4-aminopyrazolyloxy acetamide peptide analogues under mild acidic conditions such as trifluoroacetic acid (10-20%) or HCl (0.1-4.0 N) at room temperature, and the formation of unusual lactam from 4-aminopyrazolyloxy acetic acid after evaporation of solvent. This is a rare chemical event in peptide bond, which could be explored as acid-sensitive protecting group of free amines.