Copper-free Sonogashira Reaction to Modify the Tyrosine Residues on Silk Proteins

Here we explore the use of a copper-free Sonogashira reaction using a palladium catalyst to modify the tyrosine residues on silkworm silk proteins. Utilizing this cross coupling reaction, alkynes with specific functions can be introduced to silk in order to broaden the capabilities of silk proteins in biological systems. A halogenation reaction to iodinate tyrosine was first developed using the mild iodinating reagent bis(pyridine)iodonium(I) tetrafluoroborate (IPy2BF4). After that, a variety of reaction conditions were explored for the cross-coupling reactions. Qualitative information on the reaction progress collected via X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) will be presented.