The incorporation of a propargyl group to a natural product
target allows for a streamlined approach to the investigation of
structure activity relationships (SARs) and target identification
in forward chemical genetics programmes using a ‘click’-based
approach. To this end, an efficient synthesis of O-propargylated tyrosine derivatives was
designed, and these have been used in the construction of peptide motifs both (a) derived
from phage display libraries and (b) found in natural products.
The L-tyrosine derivative Y* (compound I, X=H, R=H) was incorporated into a peptide
sequence, PTTIYY, which is known to prevent the inhibition of p53 by the AG-2 protein. Y*
has been included as both the terminal and the internal tyrosine in the peptide sequence.
ELISA assays were carried out to determine how the binding of PTTIYY* and PTTIY*Y to
AG-2 compared to that of the un-marked PTTIYY sequence. The results of these assays
allowed new conclusions to be drawn regarding the important binding features of the peptide
and possible sites for further optimisation of the AG-2 binding properties of this peptide
through ‘click’ functionalisation of the modified tyrosine. The binding of the peptides
incorporating Y* was also assessed using MCF-7 breast cancer cell lysate, known to contain
the AG-2 protein. These results confirmed those seen for the purified AG-2 ELISA.
The related bromo-D-tyrosine derivative (compound I, X=Br, R=Me) has been prepared and
employed towards the synthesis of a bisebromoamide derivative. Bisebromoamide is a newly
discovered polypeptide, and a promising anti-cancer agent. The bisebromoamide derivative
contains a thiazole unit (Tzl), two N-methylated amino acids, and an oxopropyl pyrrolidine
(Opp) moiety, which is unique to bisebromoamide in natural products. The activity of this
bisebromoamide derivative will be investigated via ‘click’-based affinity chromatography
using a new supported linker recently developed within the Hulme group