A highly selective intramolecular trans-silylvinylation of internal alkynes catalyzed by RuHCl(CO)(SIMes)(PPh3) has been accomplished. The use of methyl vinyl ketone as an additive increased the efficiency of this transformation. This process was used to successfully form five-, six-, and seven-membered oxasilacycles by a formal anti-exo-dig cyclization.

A structure-activity relationship study of potent TIQ15-derived CXCR4 antagonists is reported. In this investigation, the TIQ15 side-chain was constrained to improve its drug properties. The cyclohexylamino congener was found to be a potent CXCR4 inhibitor (IC = 33 nM in CXCL12-mediated Ca flux) with enhanced stability in liver microsomes and reduced inhibition of CYP450 (2D6). The improved CXCR4 antagonist has potential therapeutic application as a single agent or combinatory anticancer therapy.

The intramolecular trans-silylruthenation of internal alkynes and subsequent insertion of vinyl boronates is described. This approach provides complete regiocontrol through a stereoselective trans-5-exo-dig cyclization which affords a tetrasubstituted olefin as a vinylsilane and a highly functionalized Z,E diene motif.

CXCR4 is a G-protein-coupled receptor that interacts with its cognate ligand, CXCL12, to synchronize many physiological responses and pathological processes. Disruption of the CXCL12-CXCR4 circuitry by small-molecule antagonists has emerged as a promising strategy for cancer intervention. We previously disclosed a hit-to-lead effort that led to the discovery of a series of tetrahydroisoquinoline-based CXCR4 antagonists exemplified by the lead compound TIQ15. Herein, we describe our medicinal-chemistry efforts toward the redesign of TIQ15 as a result of high mouse-microsomal clearance, potent CYP2D6 inhibition, and poor membrane permeability. Guided by the in vitro ADME data of TIQ15, structural modifications were executed to provide compound 12a, which demonstrated a reduced potential for first-pass metabolism while maintaining CXCR4 potency. Subsequent SAR studies and multiparameter optimization of 12a resulted in the identification of compound 25o, a highly potent, selective, and metabolically stable CXCR4 antagonist possessing good intestinal permeability and low risk of CYP-mediated drug-drug interactions.

CXCR4 is a seven-transmembrane receptor expressed by hematopoietic stem cells and progeny, as well as by ≥48 different cancers types. CXCL12, the only chemokine ligand of CXCR4, is secreted within the tumor microenvironment, providing sanctuary for CXCR4 tumor cells from immune surveillance and chemotherapeutic elimination by (1) stimulating prosurvival signaling and (2) recruiting CXCR4 immunosuppressive leukocytes. Additionally, distant CXCL12-rich niches attract and support CXCR4 metastatic growths. Accordingly, CXCR4 antagonists can potentially obstruct CXCR4-mediated prosurvival signaling, recondition the CXCR4 leukocyte infiltrate from immunosuppressive to immunoreactive, and inhibit CXCR4 cancer cell metastasis. Current small molecule CXCR4 antagonists suffer from poor oral bioavailability and off-target liabilities. Herein, we report a series of novel tetrahydroisoquinoline-containing CXCR4 antagonists designed to improve intestinal absorption and off-target profiles. Structure-activity relationships regarding CXCR4 potency, intestinal permeability, metabolic stability, and cytochrome P450 inhibition are presented.