Allosteric regulation of DNA binding and target residence time drive the cytotoxicity of phthalazinone-based PARP-1 inhibitors.

Allosteric coupling between the DNA binding site to the NAD+-binding pocket drives PARP-1 activation. This allosteric communication occurs in the reverse direction such that NAD+ mimetics can enhance PARP-1's affinity for DNA, referred to as type I inhibition. The cellular effects of type I inhibition are unknown, largely because of the lack of potent, membrane-permeable type I inhibitors. Here we identify the phthalazinone inhibitor AZ0108 as a type I inhibitor. Unlike the structurally related inhibitor olaparib, AZ0108 induces replication stress in tumorigenic cells. Synthesis of analogs of AZ0108 revealed features of AZ0108 that are required for type I inhibition. One analog, Pip6, showed similar type I inhibition of PARP-1 but was ∼90-fold more cytotoxic than AZ0108. Washout experiments suggest that the enhanced cytotoxicity of Pip6 compared with AZ0108 is due to prolonged target residence time on PARP-1. Pip6 represents a new class of PARP-1 inhibitors that may have unique anticancer properties.

A Selective C-H Deprotonation Strategy to Access Functionalized Arynes by Using Hypervalent Iodine.

Described here is an efficient method to access highly functionalized arynes from unsymmetrical aryl(mesityl)iodonium tosylate salts. The iodonium salts are prepared in a single pot from either commercially available aryl iodides or arylboronic acids. The aryne intermediates are generated by ortho-C-H deprotonation of aryl(mesityl)iodonium salt with a commercially available amide base and trapped in a cycloaddition reaction with furan in moderate to good yields. Coupling partners for the aryne intermediates beyond furan are also described, including benzyl azide and alicyclic amine nucleophiles. The regio- and chemoselectivity of this reaction is discussed and evidence for the spectator aryl ligand of the iodonium salt as a critical control element in selectivity is presented.

Unsymmetrical Aryl(2,4,6-trimethoxyphenyl)iodonium Salts: One-Pot Synthesis, Scope, Stability, and Synthetic Studies.

Diaryliodonium salts have recently attracted significant attention as metal-free-arylation reagents in organic synthesis, and efficient access to these salts is critical for advancement of their use in reaction discovery and development. The trimethoxybenzene-derived auxiliary is a promising component of unsymmetrical variants, yet access remains limited. Here, a one-pot synthesis of aryl(2,4,6-trimethoxyphenyl)iodonium salts from aryl iodides, m-CPBA, p-toluenesulfonic acid, and trimethoxybenzene is described. Optimization of the reaction conditions for this one-pot synthesis was enabled by the method of multivariate analysis. The reaction is fast (<1 h), provides a high yield of product (>85% average), and has broad substrate scope (>25 examples) including elaborate aryl iodides. The utility of these reagents is demonstrated in moderate to high yielding arylation reactions with C-, N-, O-, and S-nucleophiles including the synthesis of a liquid crystal molecule.

Base Mediated Synthesis of Alkyl-aryl Ethers from the Reaction of Aliphatic Alcohols and Unsymmetric Diaryliodonium Salts.

The base mediated coupling of aliphatic alcohol pronucleophiles with unsymmetric diaryliodonium salt electrophiles is described. This metal-free reaction is operationally simple, proceeds at mild temperature, and displays broad substrate scope to generate industrially important alkyl-aryl ethers in moderate to excellent yield. The synthetic utility of these reactions is demonstrated, and aspects of sustainability are highlighted by the use of unsymmetric aryl(mesityl)iodonium arylating reagents.