Copper-Catalyzed Decarboxylative Trifluoromethylation of Propargyl Bromodifluoroacetates

The development of efficient methods for accessing fluorinated functional groups is desirable. Herein, we report a two-step method that utilizes catalytic Cu for the decarboxylative trifluoromethylation of propargyl bromodifluoroacetates. This protocol affords a mixture of propargyl trifluoromethanes and trifluoromethyl allenes

Intracellular Delivery of Rapamycin From FKBP Elastin-Like Polypeptides Is Consistent With Macropinocytosis

Rapamycin (Rapa) is a highly potent drug; however, its clinical potential is limited by poor solubility, bioavailability, and cytotoxicity. To improve Rapa delivery, our team has fused the cognate protein receptor for Rapa, FKBP12, to high molecular weight elastin-like polypeptides (ELPs). One construct, FAF, includes an FKBP domain at each termini of an ELP. In a recent report, FAF/Rapa outperformed a family of related carriers with higher tumor accumulation and efficacy. Despite apparent efficacy, an explanation for how FAF carries Rapa into cells has not been elucidated. This manuscript explores the intracellular fate of FAF in MDA-MB-468, a triple negative (ER-/PR-/HER2-) breast cancer line. Based on a lack of displacement by excess unlabeled FAF, no evidence was found for the involvement of a receptor in cell-surface binding. Cellular association showed no dose-dependent saturation at concentrations up to 100 μM, which is consistent with uptake through fluid phase endocytosis. FAF does colocalize with dextran, a marker of fluid phase endocytosis. Upon internalization, both FAF and dextran target low pH intracellular compartments similarly. Despite likely exposure to lysosomal pH and proteolytic activity, intracellular FAF is eliminated from cells with a relatively long half-life of 17.7 and 19.0 h by confocal microscopy and SDS-PAGE respectively. A split luciferase reporter assay demonstrated that FAF delays the cytosolic access of Rapa in comparison to free drug by 30 min. A specific macropinocytosis inhibitor, amiloride, completely inhibits the cytosolic delivery of Rapa from FAF. Each of these results are consistent with macropinocytosis as the mechanism of cellular uptake necessary for the hand-off of Rapa from FKBP-based drug carriers like FAF to endogenous FKBP12 in the cytosol

Ligand-controlled Regioselective Cu-Catalyzed Trifluoromethylation to Generate Trifluoromethylallenes

“Cu–CF3” species have been used historically for a broad spectrum of nucleophilic trifluoromethylation reactions. Although recent advancements have employed ligands to stabilize and harness the reactivity of this key organometallic intermediate, the ability of a ligand to differentiate a regiochemical outcome of a Cu–CF3-mediated or -catalyzed reaction has not been previously reported. Herein, we report the first example of a Cu-catalyzed trifluoromethylation reaction in which a ligand controls the regiochemical outcome. More specifically, we demonstrate the ability of bipyridyl-derived ligands to control the regioselectivity of the Cu-catalyzed nucleophilic trifluoromethylation reactions of propargyl electrophiles to generate trifluoromethylallenes. This method provides a variety of di-, tri- and tetra-substituted trifluoromethylallenes, which can be further modified to generate complex fluorinated substructures

Ligand-Controlled Regioselective Copper-Catalyzed Trifluoromethylation To Generate (Trifluoromethyl)allenes

“Cu–CF₃” species have been used historically for a broad spectrum of nucleophilic trifluoromethylation reactions. Although recent advancements have employed ligands to stabilize and harness the reactivity of this key organometallic intermediate, the ability of a ligand to differentiate a regiochemical outcome of a Cu–CF₃-mediated or -catalyzed reaction has not been previously reported. Herein, we report the first example of a Cu-catalyzed trifluoromethylation reaction in which a ligand controls the regiochemical outcome. More specifically, we demonstrate the ability of bipyridyl-derived ligands to control the regioselectivity of the Cu-catalyzed nucleophilic trifluoromethylation reactions of propargyl electrophiles to generate (trifluoromethyl)­allenes. This method provides a variety of di-, tri-, and tetrasubstituted (trifluoromethyl)­allenes, which can be further modified to generate complex fluorinated substructures

Bifunctional Elastin-like Polypeptide Nanoparticles Bind Rapamycin and Integrins and Suppress Tumor Growth in Vivo

Recombinant protein–polymer scaffolds such as elastin-like polypeptides (ELPs) offer drug-delivery opportunities including biocompatibility, monodispersity, and multifunctionality. We recently reported that the fusion of FK-506 binding protein 12 (FKBP) to an ELP nanoparticle (FSI) increases rapamycin (Rapa) solubility, suppresses tumor growth in breast cancer xenografts, and reduces side effects observed with free-drug controls. This new report significantly advances this carrier strategy by demonstrating the coassembly of two different ELP diblock copolymers containing drug-loading and tumor-targeting domains. A new ELP nanoparticle (ISR) was synthesized that includes the canonical integrin-targeting ligand (Arg-Gly-Asp, RGD). FSI and ISR mixed in a 1:1 molar ratio coassemble into bifunctional nanoparticles containing both the FKBP domain for Rapa loading and the RGD ligand for integrin binding. Coassembled nanoparticles were evaluated for bifunctionality by performing in vitro cell-binding and drug-retention assays and in vivo MDA-MB-468 breast tumor regression and tumor-accumulation studies. The bifunctional nanoparticle demonstrated superior cell target binding and similar drug retention to FSI; however, it enhanced the formulation potency, such that tumor growth was suppressed at a 3-fold lower dose compared to an untargeted FSI–Rapa control. This data suggests that ELP-mediated scaffolds are useful tools for generating multifunctional nanomedicines with potential activity in cancer