Synthesis of hemithioindigo-based chromopeptides by using the Tmb auxiliary in native chemical ligation studies.

The 4,5,6-trimethoxy-2-mercaptobenzyl auxiliary was used in auxiliary-based native chemical ligation reactions with Boc-protected pHTI and mHTI ω-amino acid thioesters 2a,b for the construction of small hemithioindigo (HTI)-based chromopeptides 6a,b with a class 1 PDZ binding motif. While reversible tris(2-carboxyethyl)phosphine (TCEP)-HTI adduct formation required moderate use of access TCEP, the Na ascorbate concentration was broadly varied for optimization of the reaction conditions. In the studies presented, the mHTI ω-amino acid thioester 2b proved to be slightly less reactive than the pHTI ω-amino acid thioester 2a.

Light-Switchable Peptides with a Hemithioindigo Unit: Peptide Design, Photochromism, and Optical Spectroscopy.

This Minireview focuses on the hemithioindigo photoswitch and its use for the reversible control of three-dimensional peptide structure and related biological functions. Both the general design aspects and biophysical properties of various hemithioindigo-based chromopeptides are summarized. Hemithioindigo undergoes reversible Z→E photoisomerization after absorption of visible light.