Total Synthesis of Darobactin A.

The collaborative total synthesis of darobactin A, a recently isolated antibiotic that selectively targets Gram-negative bacteria, has been accomplished in a convergent fashion with a longest linear sequence of 16 steps from d-Garner's aldehyde and l-serine. Scalable routes toward three non-canonical amino acids were developed to enable the synthesis. The closure of the bismacrocycle was realized through sequential, halogen-selective Larock indole syntheses, where the proper order of cyclizations proved crucial for the formation of the desired atropisomer of the natural product.

Selective Formation of Functionalized α-Quaternary Malononitriles toward 5,5-Disubstituted Pyrrolopyrimidinones.

A modular, selective approach to complex α-tertiary substituted malononitriles is reported. The method takes advantage of ß-ester-substituted α,α-dinitrile alkenes as highly reactive, chemoselective electrophiles for 1,4-additions with organometallic nucleophiles to produce functionally and sterically dense all-carbon quaternary centers. In the presence of a chiral ester auxiliary bearing an aromatic ring, the 1,4-addition occurs with good to excellent selectivity due to favorable cation-π interactions. The highly functionalized malononitriles represent versatile building blocks and can be applied toward efficient, highly selective syntheses of 5,5-disubstituted pyrrolopyrimidinones.

The protecting-group free selective 3'-functionalization of nucleosides.

The direct and chemoselective 3'-phosphoramidation, phosphorylation and acylation of nucleosides are described. Upon the discovery of a novel 3'-phosphorylamidation of therapeutic nucleoside analogues with DBU, we explored the mechanism of this rare selectivity through a combination of NMR spectroscopy and computational studies. The NMR and computational findings allowed us to develop a predictive computational model that accurately assesses the potential for 3'-functionalization for a broad range of nucleosides and nucleoside mimetics. The synthetic utility of this model was exemplified by demonstration on a broad scope of nucleosides and electrophiles yielding targets that were previously only accessible via a protection/deprotection sequence or an enzymatic approach.

Discovery and optimization of 2-pyridinone aminal integrase strand transfer inhibitors for the treatment of HIV.

HIV integrase strand transfer inhibitors (InSTIs) represent an important class of antiviral therapeutics with proven efficacy and excellent tolerability for the treatment of HIV infections. In 2007, Raltegravir became the first marketed strand transfer inhibitor pioneering the way to a first-line therapy for treatment-naïve patients. Challenges with this class of therapeutics remain, including frequency of the dosing regimen and the genetic barrier to resistance. To address these issues, research towards next-generation integrase inhibitors has focused on imparting potency against RAL-resistent mutants and improving pharmacokinetic profiles. Herein, we detail medicinal chemistry efforts on a novel class of 2-pyridinone aminal InSTIs, inpsired by MK-0536, which led to the discovery of important lead molecules for our program. Systematic optimization carried out at the amide and aminal positions on the periphery of the core provided the necessary balance of antiviral activity and physiochemical properties. These efforts led to a novel aminal lead compound with the desired virological profile and preclinical pharmacokinetic profile to support a once-daily human dose prediction.

Discovery of 2-Pyridinone Aminals: A Prodrug Strategy to Advance a Second Generation of HIV-1 Integrase Strand Transfer Inhibitors.

The search for new molecular constructs that resemble the critical two-metal binding pharmacophore required for HIV integrase strand transfer inhibition represents a vibrant area of research within drug discovery. Here we present the discovery of a new class of HIV integrase strand transfer inhibitors based on the 2-pyridinone core of MK-0536. These efforts led to the identification of two lead compounds with excellent antiviral activity and preclinical pharmacokinetic profiles to support a once-daily human dose prediction. Dose escalating PK studies in dog revealed significant issues with limited oral absorption and required an innovative prodrug strategy to enhance the high-dose plasma exposures of the parent molecules.

Development of a novel tricyclic class of potent and selective FIXa inhibitors.

Using structure based drug design, a novel class of potent coagulation factor IXa (FIXa) inhibitors was designed and synthesized. High selectivity over FXa inhibition was achieved. Selected compounds were evaluated in rat IV/PO pharmacokinetic (PK) studies and demonstrated desirable oral PK profiles. Finally, the pharmacodynamics (PD) of this class of molecules were evaluated in thrombin generation assay (TGA) in Corn Trypsin Inhibitor (CTI) citrated human plasma and demonstrated characteristics of a FIXa inhibitor.

Development of a palladium-catalyzed α-arylation of cyclopropyl nitriles.

1,1-Disubstituted aryl cyclopropyl nitriles are useful moieties in biologically active compounds and provide access to a range of cyclopropyl derivatives. Herein, we describe the development of a palladium-catalyzed α-arylation of cyclopropyl, cyclobutyl, and cyclopentyl nitriles that affords these functional groups in one step from a variety of aryl bromides in good to excellent yields. Furthermore, we demonstrate the transformation of aryl cyclopropyl nitriles into aryl trifluoromethyl cyclopropanes.