Synthesis of 6H-telluro[2,3-b]pyrrole Towards the Synthesis of [6,7]Telluro-L-Tryptophan ([6,7]TeTrp)
Heavy-atom containing amino acid analogs have proven to be helpful in protein structure determination, which is imperative for drug design, as well as the discovery and etiology of diseases caused by changes in protein structure. Protein structures are able to be analyzed via x-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and mass spectroscopy. Multiwavelength anomalous diffraction (MAD) allows for improved resolution by utilizing heavy atoms, such as selenium and tellurium, as they provide better x-ray diffraction data. In addition, tellurium-127 can be incorporated to better understand the protein structure and function by NMR spectroscopy. Improvements in the synthesis of a tellurium-containing tryptophan analog ([6,7]TeTrp) are shown through a series of reactions. The synthesis of the telluropyrrole ring consists of a key annulation step, which must occur in the presence of a Lewis acid catalyst. Future work includes the determination of which acids produce a larger product size with greater percent yields during annulation.
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