Synthesis and characterization of a photocleavable collagen-like peptide

On resin fragment condensation was used to assemble a photoreactive collagen-like peptide; photolysis occurs at the N-peptidyl-nitroindoline bonds.

Synthesis of Monofunctionalized Calix[5]arenes

Seven OH-free and O-permethylated monofunctionalized calix[5]arenes carrying either additional methyl or tert-butyl groups are prepared following fragment condensation protocols. This strategy proves to be superior to previous approaches. Calix[5]arenes with free OH groups all adopt a cone conformation stabilized by a seam of hydrogen bonds at the lower rim. Post-condensation modifications, i.e., methylation of phenolic OH groups or functional group interconversions can also be achieved. Bulky tert-butyl groups are also found to stabilize the cone conformations of O-methylated compounds. These compounds offer versatile functional groups that make these concave molecules interesting building blocks for the synthesis of more sophisticated molecular architectures.

Ynamide: A New Coupling Reagent for Amide and Peptide Synthesis

The discovery and application of ynamide coupling reagents is highlighted with a brief summary of the development history of coupling reagents in amide and peptide synthesis. As novel coupling reagents, ynamides are not only effective for simple amide and dipeptide synthesis but also can be used for peptide fragment condensation. More importantly, no racemization was detected during the activation of α-chiral carboxylic acids by employing ynamide coupling reagents.1 Introduction2 Carbodiimide Coupling Reagents3 Uronium/Guanidinium Salt Coupling Reagents4 Phosphonium Salt Coupling Reagents5 Ethoxyacetylene as a Coupling Reagent6 Ynamine Coupling Reagents7 Ynamide Coupling Reagents8 Summary and Outlook