Galactosylsphingamides: new \u03b1-GalCer analogues to probe the F\u2019-pocket of CD1d

Joren Guillaume,Soumya G Remesh,Mathy Froeyen,Tine Decruy,Martijn D P Risseeuw,Jonas Janssens,Dirk M Zajonc,Jing Wang,Dirk Elewaut,Serge Van Calenbergh

doi:10.1038/s41598-017-04461-7

Abstract

Invariant Natural Killer T-cells (iNKT-cells) are an attractive target for immune response modulation, as upon CD1d-mediated stimulation with KRN7000, a synthetic α-galactosylceramide, they produce a vast amount of cytokines. Here we present a synthesis that allows swift modification of the phytosphingosine side chain by amidation of an advanced methyl ester precursor. The resulting KRN7000 derivatives, termed α-galactosylsphingamides, were evaluated for their capacity to stimulate iNKT-cells. While introduction of the amide-motif in the phytosphingosine chain is tolerated for CD1d binding and TCR recognition, the studied α-galactosylsphingamides showed compromised antigenic properties.

Highlights

Invariant natural killer T-cells are a small set of glycolipid reactive T-cells that bridge innate and adaptive immunity
As shown in the retrosynthetic analysis (Fig. 3), the α-galactosylsphingamides (5a-h, 6–9d and 9f) can be accessed from methyl ester 10, which is obtained through Lewis acid catalyzed glycosylation of glycosyl acceptor 12
A series of α-GalCer analogues featuring an amide bond in the phytosphingosine were synthesized

Summary

Introduction

Invariant natural killer T-cells (iNKT-cells) are a small set of glycolipid reactive T-cells that bridge innate and adaptive immunity They display characteristics of both the NK cell lineage (mouse NK1.1, human CD161) and conventional thymus-derived T-cells[1]. A common strategy for the synthesis of α-GalCer analogues modified in the phytosphingosine moiety relies on the Wittig olefination on L-Garner’s aldehyde, followed by stereoselective dihydroxylation of the Z-double bond furnishing the required d-ribo stereochemistry[14, 22]. This approach may afford high stereoselectivity, it inevitably leads to minor unwanted isomers thereby lowering the overall yield and forcing demanding purification steps ahead in the synthesis

Methods

Results

Conclusion