Scale-Up Preparation\nof Best-In-Class Orally Bioavailable\nCXCR4 Antagonist EMU-116 in an Academic Setting

CXCR4 is a seven-transmembrane chemokine receptor that\nis intimately\ninvolved in stem cell niche maintenance and immune cell trafficking.\nAmong several other pathophysiological states for which CXCR4 mis\nregulation is implicated, various hematological malignancies and solid\ntumors hijack this chemokine network by dramatically overexpressing\nCXCR4 and its cognate chemokine ligand CXCL12. Upregulation of the\nCXCR4/CXCL12 axis in cancer drives tumor progression through several\nmechanisms, which makes CXCR4 a promising target for the development\nof anticancer therapeutics. Herein, we report the preparative scale\nsynthesis of a novel, best-in-class, orally bioavailable small molecule\nCXCR4 antagonist, EMU-116. Two synthetic strategies for production\nof EMU-116 were pursued. While the first discovery-focused synthesis\nfacilitated late-stage diversification to drive structure–activity\nrelationship determinations, the second process-focused synthesis\ndelivered EMU-116 more efficiently in higher overall yield with enhanced\nstereocontrol. For both synthetic routes, Buchwald–Hartwig\namination of key aryl bromide intermediates enabled installation of\nthe <i>N</i>-methylpiperazine appendage of EMU-116. Synthetic\nmethods devised to prepare (<i>R</i>)-9-bromo-1,5,10,10<i>a</i>-tetrahydro-3<i>H</i>-oxazolo[3,4<i>-b</i>]isoquinolin-3-one, the key aryl bromide intermediate required for\nthe process-focused synthesis, are reported. In addition, an improved\npreparative method of known synthon (<i>S</i>)–<i>N</i>-methyl-5,6,7,8-tetrahydroquinolin-8-amine is highlighted\nby elevated overall yield, enhanced diastereoselectivity, and robust\npurification by crystallization. Further elaboration of these two\nintermediates, coupling via reductive amination to furnish the full\nEMU-116 scaffold, removal of protecting groups, and final product\npurification techniques are also reported. Overall, the synthetic\nmethods described herein enabled reliable and efficient production\nof multigram quantities of EMU-116 and are anticipated to be amenable\nto larger scale production.