Synthesis and structural characterization of amino acid and peptide derivatives featuring N-(p-bromobenzoyl) substituents as promising connection unit for bio-inspired hybrid compounds

Using a sequence of activation, blocking and peptide coupling procedures, a series of ten amino acid and peptide derivatives 1–6 (a, b, respectively) featuring a p-bromobenzoyl substituent attached to the amino group of the parent compound has been synthesized. X-ray crystal structures of two corresponding amino acid (1a, 1b), two amino acid ester (3a, 3b) and three peptide ester derivatives (4a, 4b, 5b) are reported, with the amide and peptide bonds of the molecules all being planar and trans configurated. Intramolecular interactions dominating the packing motifs and thus giving rise to the formation of strands (1a, 3a, 3b, 4a, 4b), molecular pairs (1b) or sheets (5b) derive from N–H⋯O contacts, being further assisted by O–H⋯O and weaker C–H⋯O interactions, while bromo involved contacts are of minor importance.

► N-(p-bromobenzoyl) amino acids and peptides were synthesized and characterized. ► The compounds are promising building blocks for bioconjugate formation. ► Molecular and packing structures were determined by X-ray crystallography. ► The packing structures are dominated by N–H⋯O hydrogen bonding interactions. ► For the formation of sheet motifs at least a tripeptide derivative is necessary.