Reversible Covalent End-Capping of Collagen Model Peptides.

The combination of supramolecular aggregation of collagen model peptides with reversible covalent end-capping of the formed triple helix in a single experimental set-up yielded minicollagens, which were characterized by a single melting temperature. In spite of the numerous possible reaction intermediates, a specific synthetic collagen with a leading, middle and trailing strand is formed in a highly cooperative self-assembly process.

Synthetic Marine Sponge Collagen by Late-Stage Dihydroxylation.

Based on the observation that an increased substrate size is paralleled by an enhanced diastereoselectivity, a late-stage dihydroxylation protocol toward the 21mer CMP (collagen model peptide) Ac-(Pro-Hyp-Gly)-Pro-Dyp-Gly-(Pro-Hyp-Gly)-NH is presented. C3 and C4 hydroxylation have a converse effect on the triple-helical stability of collagen. Their combined influence on the melting temperature was studied by NMR spectroscopy.

Scaling the Amphiphilic Character and Antimicrobial Activity of Gramicidin S by Dihydroxylation or Ketal Formation.

The acid lability of aliphatic ketals, which often serve as protection groups for 1,2-diols, is influenced by their local structural environment. The acetonide of the protected amino acid cis-dihydroxyproline (Dyp) is a typical protecting group cleavable by traces of TFA. The tricyclic acetonide of the dipeptide d-Hot═Tap is resistant to TFA and thus can serve as a bioorthogonal modification of bioactive peptides.