Strategies to Synthesize Template-Constrained Macrocycles with Improved Pharmacological Properties – from Tryptophan Alkylations to cIAP-Selective Antagonists & Glycosylated Peptidomimetics

Peptide-derived macrocycles are a potentially rich source of biologically active lead structures, which are capable of recapitulating a therapeutic protein-protein surface interaction. Their three-dimensional shape influences both the macrocycle’s binding to protein surfaces as well as its pharmacological properties. While other cyclization methods have focused on ring formation to yield singular products from a given peptide, small template molecules can also be used as hydrophobic scaffolds to engage and cyclize unprotected peptides in order access regioisomeric variants of each peptide sequence. In this way, we hope to engineer improved pharmacological and therapeutic properties of bioactive or bio-inspired peptides. These designed template molecules incrementally constrain peptide structure through systematic cyclizations to restrict conformation and stabilize against degradation by metabolic enzymes. These hybrid molecules are intended to retain molecular recognition elements in the biopolymer while displaying that functionality as part of stable polycycles having defined shapes and improved pharmacological properties. Chapter 2 covers Friedel-Crafts macrocinnamylations of tryptophan-containing peptides, specifically studying the endo-pyrroloindoline products produced from such reactions. We found this product to be sensitive to acidic conditions, which lead to regioisomeric rearrangement products. We studied the kinetics of this rearrangement both experimentally and computationally. In Chapter 3, the synthesis and use of a new, four-armed template molecule, which now bears a terminal alkyne are detailed. We utilized the terminal alkyne as a site for glycosylation through a copper-catalyzed Huisgen cycloaddition as well as a dimerization event. This now third generation template afforded regioisomeric macrocyclic products derived from the second mitochondrial activator of caspases (Smac) N-terminus, which displayed differing affinities for inhibitor of apoptosis proteins (IAPs). In Chapter 4, methods to engage the terminal alkyne of the third generation template in a unimolecular reaction are investigated. Although a bicyclization reaction eluded us, the data discussed therein may provide insight into further endeavors

Strategies to Synthesize Template-Constrained Macrocycles with Improved Pharmacological Properties – from Tryptophan Alkylations to cIAP-Selective Antagonists & Glycosylated Peptidomimetics

Peptide-derived macrocycles are a potentially rich source of biologically active lead structures, which are capable of recapitulating a therapeutic protein-protein surface interaction. Their three-dimensional shape influences both the macrocycle’s binding to protein surfaces as well as its pharmacological properties. While other cyclization methods have focused on ring formation to yield singular products from a given peptide, small template molecules can also be used as hydrophobic scaffolds to engage and cyclize unprotected peptides in order access regioisomeric variants of each peptide sequence. In this way, we hope to engineer improved pharmacological and therapeutic properties of bioactive or bio-inspired peptides. These designed template molecules incrementally constrain peptide structure through systematic cyclizations to restrict conformation and stabilize against degradation by metabolic enzymes. These hybrid molecules are intended to retain molecular recognition elements in the biopolymer while displaying that functionality as part of stable polycycles having defined shapes and improved pharmacological properties. Chapter 2 covers Friedel-Crafts macrocinnamylations of tryptophan-containing peptides, specifically studying the endo-pyrroloindoline products produced from such reactions. We found this product to be sensitive to acidic conditions, which lead to regioisomeric rearrangement products. We studied the kinetics of this rearrangement both experimentally and computationally. In Chapter 3, the synthesis and use of a new, four-armed template molecule, which now bears a terminal alkyne are detailed. We utilized the terminal alkyne as a site for glycosylation through a copper-catalyzed Huisgen cycloaddition as well as a dimerization event. This now third generation template afforded regioisomeric macrocyclic products derived from the second mitochondrial activator of caspases (Smac) N-terminus, which displayed differing affinities for inhibitor of apoptosis proteins (IAPs). In Chapter 4, methods to engage the terminal alkyne of the third generation template in a unimolecular reaction are investigated. Although a bicyclization reaction eluded us, the data discussed therein may provide insight into further endeavors

Stabilization of the Max Homodimer with a Small Molecule Attenuates Myc-Driven Transcription

The transcription factor Max is a basic-helix-loop-helix leucine zipper (bHLHLZ) protein that forms homodimers or interacts with other bHLHLZ proteins, including Myc and Mxd proteins. Among this dynamic network of interactions, the Myc/Max heterodimer has crucial roles in regulating normal cellular processes, but its transcriptional activity is deregulated in a majority of human cancers. Despite this significance, the arsenal of high-quality chemical probes to interrogate these proteins remains limited. We used small molecule microarrays to identify compounds that bind Max in a mechanistically unbiased manner. We discovered the asymmetric polycyclic lactam, KI-MS2-008, which stabilizes the Max homodimer while reducing Myc protein and Myc-regulated transcript levels. KI-MS2-008 also decreases viable cancer cell growth in a Myc-dependent manner and suppresses tumor growth in vivo. This approach demonstrates the feasibility of modulating Max with small molecules and supports altering Max dimerization as an alternative approach to targeting Myc.National Cancer Institute (Grant R01-CA160860)National Cancer Institute (Grant P30-CA14051)National Cancer Institute (Grant U01-CA176152)National Cancer Institute (Grant CA170378PQ2)National Institutes of Health (Grant CA170378PQ2