Convergent synthesis of potent peptide inhibitors of the Grb2-SH2 domain by palladium catalyzed coupling of a terminal alkyne

A facile and convenient sequential homobimetallic catalytic approach towards β-methylstyrenes. A one-pot Stille cross-coupling/isomerization strategy

A one-pot approach towards β-methylstyrenes is reported. The transformation involves a Stille cross-coupling reaction of aryl halides with allyltributylstannane, followed by an in situ Pd-catalyzed double bond conjugative migration.

Utilization of achiral alkenyl amines for the preparation of high affinity Grb2 SH2 domain-binding macrocycles by ring-closing metathesis

A family of previously reported ring-closing metathesis (RCM)-derived macrocycles that exhibit potent Grb2 SH2 domain-binding affinity is characterized by stereoselectively-introduced upper ring junctions that bear bicyclic aryl substituents. However, the synthetic complexity of these macrocycles presents a potential limit to their therapeutic application. Therefore, the current study was undertaken to simplify these macrocycles through the use of achiral 4-pentenylamides as ring-forming components. A series of macrocycles (5a-f) was prepared bearing both open and cyclic constructs at the upper ring junction. The Grb2 SH2 domain-binding affinities of these macrocycles varied, with higher affinities being obtained with cyclo-substituents. The most potent analogue (5d) contained a cyclohexyl group and exhibited Grb2 SH2 domain-binding affinity (K(D) = 1.3 nM) that was nearly equal to the parent macrocycle (2), which bore a stereoselectively-introduced naphthylmethyl substituent at the upper ring junction (K(D) = 0.9 nM). The results of this study advance design considerations that should facilitate the development of Grb2 SH2 domain-binding antagonists.

Development of Grb2 SH2 Domain Signaling Antagonists: A Potential New Class of Antiproliferative Agents

Aberrant signaling through protein-tyrosine kinase (PTK)-dependent pathways is associated with several proliferative diseases. Accordingly, PTK inhibitors are being developed as new approaches for the treatment of certain cancers. Growth factor receptor bound protein 2 (Grb2) is an important downstream mediator of PTK signaling that serves obligatory roles in many pathogenic processes. One of the primary functions of Grb2 is to bind to specific phosphotyrosyl (pTyr)-containing sequences through its Src homology 2 (SH2) domain. Agents that bind to the Grb2 SH2 domain and prevent its normal function could disrupt associated PTK signaling and serve as alternatives to kinase-directed inhibitors. Starting from the X-ray crystal structure of a lead peptide bound to the Grb2 SH2 domain, this review will summarize important contributions to these efforts. The presentation will be thematically arranged according to the region of peptide modified, proceeding from the N-terminus to the C-terminus, with a special section devoted to aspects of conformational constraint.

Synthesis of Alkyne-Bridged Cyclic Tripeptides toward Constrained Mimics of Vancomycin

The synthesis of a range of highly constrained cyclic tripeptides has been performed using either an intramolecular Sonogashira coupling or a macrolactamization as the final ring-closing reaction. Our approach gives access to rigidified 15-membered peptidic macrocycles based on the central ring system of vancomycin. Tripeptides 3a-c and dipeptide 11 were cyclized via an intramolecular Sonogashira reaction, and the cyclic peptides 4a-c and 15a were obtained in 6-23% yield. In contrast, macrolactamization of 12 and 17 resulted in the desired peptidic macrocycles 15b and 18 with 54-61% yield. Modeling studies hint at a distorted triple bond, which explains the low yield of the Sonogashira-based cyclization. Moreover, modeling data also showed that this class of peptidic macrocycles formed a cavity-like structure in which guest molecules may bind.

Synthesis of Conformationally Constrained C-Glycosyl α- and β-Amino Acids and Sugar−Carbamino Sugar Hybrids via Diels−Alder Reaction

[structure: see text] Sugar-derived dienes undergo Diels-Alder reactions with methyl alpha-nitro acrylate and ethyl beta-nitro acrylate to form the corresponding cycloadducts which have been converted into conformationally constrained C-glycosyl alpha- and beta-amino acids. Further, these beta-amino acids are converted into sugar-carbamino sugar hybrid molecules.

Utilization of a beta-aminophosphotyrosyl mimetic in the design and synthesis of macrocyclic Grb2 SH2 domain-binding peptides

Grb2 SH2 domains are protein-docking modules that exert important functions in both normal and pathogenic signal transduction processes. Development of synthetic Grb2 SH2 domain binding ligands is being pursued by several groups as potential new therapies for a variety of diseases, including certain cancers. In these efforts, macrocyclization has been successfully utilized to take advantage of preferential recognition by Grb2 SH2 domains of ligands in beta-bend conformations. Recent examples of this approach include olefin-metathesis-derived macrocycles that employ ring closure at the beta-position of key pTyr-mimicking residues. In the current study, a novel phosphatase-stable beta-amino-pTyr mimetic designated "Pmp(beta)" was utilized to prepare variants of previously reported olefin-metathesis-derived macrocycles. An initial set of simplified cyclic peptides lacking key naphthyl side chain functionality was first synthesized to determine optimum ring size, with results indicating that a four-unit ring-closing segment was appropriate. On the basis of these findings, macrolactamization was undertaken with a more highly functionalized, naphthyl-containing gamma-amino acid analogue. The resulting cyclic beta-amino peptide is the first of a new class of pTyr-mimetic-containing ligands that may have utility in the development of antagonists of both Grb2 SH2 domains and other pTyr-dependent signaling systems.