Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)
Marnie Kotlyar - Hunter College
Co-Author(s): Steven Truong, Hunter College, New York, NY; David Mootoo, Hunter College, New York, NY
KRN7000, also called alpha-galactosylceramine (α-GalCer), is an immunostimulatory glycolipid that comprises an α-O-galactose moiety linked to the C1 position of 2-hexacosanamido-1,3,4-trihydroxy, C-18 lipid chain. CD1d, a protein on the surface of the antigen-presenting cells (APCs) binds to KRN7000 and the binary complex is presented to the T cell receptor (TCR) on invariant natural killer T (iNKT) cells. This leads to activation of Th1 and Th2 cytokines, which induce inflammatory and immunomodulatory responses, respectively1. Regulating Th1/Th2 balance is a promising strategy to combat foreign pathogens, cancer, and certain autoimmune disorders. To this end, KRN7000 analogues with a clear Th1 or Th2 bias and measured potency are needed for clinical development. Thus the design and immunological evaluation of new analogues of KRN7000 is of considerable interest. In this context, certain C-glycosides (analogues in which the glycoside oxygen is replaced with a carbon substituent) have shown a high Th1 response2. Additionally, analogues with fluorine in the lipid segment may lead to novel cytokine profiles3. However, it is not clear how these structural changes induce a particular cytokine response. Accordingly, the goal of this project is the synthesis of novel fluorinated C-glycosides of KRN7000 for use as mechanistic probes, and as leads for drug development. To this end, we have designed a synthetic strategy that centers on the reaction of C-glycoside crotylborinates and lipid derived amines. This reaction gives a stereochemically complex glycolipid product that can be transformed to our fluorinated C-glycoside target compounds. As a test of this methodology, a C-glycosylborinate was prepared from the reaction of the palladium chloride promoted reaction of an allylic chloride precursor and bis(pinacolato)diboron. A simple lipid amine was also prepared from N-benzylamine and heptanal. Reactions were monitored by thin-layer chromatography (TLC), and reaction products were purified by flash column chromatography (FCC) and analyzed using nuclear magnetic resonance spectroscopy (NMR). Our current work is focused on the pivotal reaction of the crotylborinate and the imine, and the development of decarboxylative fluorination strategies for converting the reaction product to fluorinated C-glycosides of KRN7000. Subsequently, we will use fluorinated glycosylborinates and more substituted lipid imines for synthesis of a library of KRN7000 analogues. In future studies, the immunological properties of these molecules will be evaluated, starting with determination of the cytokine profiles that are elicited in mice. These synthetic studies are relevant to the synthesis of other classes of complex glycomimetics, and the structure-activity data from the biological investigations will provide insight on the molecular basis of these glycolipids, and potential clinical agents. References: 1. Recognition of CD1d restricted antigens by natural killer T cells. Rossjohn, J.; Pellicci D.G.; Patel O.; Gapin L.; Godfrey D.I.. Nat. Rev. Immun. 2012, 12, 845-857. 2. Stimulation of natural killer T cells by glycolipids. Anderson, B. L.; Teyton, L.; Bendelac, A.; Savage, P. B. Molecules 2013, 18, 15662-15688. 3. The many roles for fluorine in medicinal chemistry. Hagmann, W.K. J. Med. Chem. 2008, 51, 4359-4369.
Funder Acknowledgement(s): NSF
Faculty Advisor: David Mootoo, email@example.com
Role: I performed all the chemical syntheses and analyses conducted in this study.