N-( p-Ethynylbenzoyl) derivatives of amino acid and dipeptide methyl esters – Synthesis and structural study

► The synthesis of N-( p-ethynylbenzoyl) amino acid and dipeptide methyl esters is described. ► The compounds are promising building blocks for the generation of bioconjugate structures. ► Molecular and packing structures were determined by X-ray crystallography. ► The packing structures are dominated by N H⋯O hydrogen bonding interactions. ► Within the packing structures characteristic strand motifs are formed. A series of N-( p-ethynylbenzoyl) derivatives ( 1–4) of the amino acids glycine and l-alanine as well as the dipeptides glycylglycine and l-alanylglycine has been synthesized via a two-step reaction sequence including the reaction of an appropriate N-( p-bromobenzoyl) precursor with trimethylsilylacetylene followed by deprotection of the trimethylsilyl protecting group, respectively. X-ray crystal structures of the amino acid and dipeptide methyl esters 1–4 are reported. The amide and peptide bonds within each molecular structure are planar and adopt the trans-configuration. The packing structures are governed by N H⋯O interactions leading to the formation of characteristic strand motifs. Further stabilization results from weaker C H⋯O and C H⋯π contacts.