Chemical and Biomedical Motifs of the Reactions of Hydroxymethylphosphines with Amines, Amino Acids, and Model Peptides

The reactions of tris(hydroxymethyl)phosphine (THP, 1), 1,2-bis(bis(hydroxymethyl)phosphino)benzene (HMPB, 2), and 1,2-bis(bis(hydroxymethyl)phosphino)ethane (HMPE, 3) with various amines including amino acids and model peptides have been explored. The reactions of these multifunctional phosphines with excess amino acids unexpectedly produced monomeric products. The reaction of THP with excess glycine produced THP(glycine)₃ (4) in high yield. The reactions of HMPB with the secondary amines N-methylaniline and diethylamine produced the compounds HMPB(N-methylaniline)₄ (5) and HMPB(diethylamine)₄ (6), respectively. However, the reactions of HMPB and HMPE with excess glycine produced trans annular-bonded bicyclic compounds HMPB(glycine)₂ (7) and HMPE(glycine)₂ (10). The reactions of HMPB with excess alanine and glycylglycylglycine were also explored to determine the generality of the reactions and correspondingly yielded the novel heterocyclic compounds HMPB(alanine)₂ (8) and HMPB(gly-gly-gly)₂ (9), respectively. The products are oxidatively stable in air and under a wide pH range. All of the new compounds have been characterized by a combination of analytical and spectroscopic techniques, and the molecular structures of compounds 4, 5, 7, and 10 have been confirmed by single-crystal X-ray diffraction studies.