Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis (TB), is one of the most successful pathogens on earth with an estimate of 10 million newly infected people and 1.6 million deaths worldwide only in 2018. The molecular players responsible for the high virulence and resistance of Mtb are still to be fully uncovered. Trehalose glycolipids, the most abundant glycolipids on the surface of the mycobacterial cell wall, were first discovered in the early 1950s and have since then been the subject of study due to their interesting immunomodulatory properties.
In 2009 Ishikawa et al. identified trehalose dimycolate and its analogue trehalose dibehenate as ligands for Mincle (macrophage induced Ca2+-dependent lectin). This receptor and its ligands seems to be involved in TB-derived granulomatosis. Several recent studies have investigated the phenotype of Mincle-deficient mice in mycobacterial infection, yielding divergent results in terms of a role for Mincle in host resistance. 
It has been shown that varying the fatty acid chain length on the trehaloses can strongly influence the biological activity. Further research helped to identify other glycolipids as ligands for Mincle and suggested higher binding affinities to the receptor. 
In this study we report the synthesis of trehalose dimycolate and glucose monomycolate analogues, equipped with a ligation handle for further conjugation to Mtb derived peptidic epitopes. The synthetic strategy for the generation of these glycolipids is based on a TMS-protecting group strategy and Steglich esterification approach. The enantiomeric fatty acids contained in compounds D and E (Fig 1) are synthesized starting from the same pseudoephedrine derivative via two stereo-divergent approaches: a Meyers alkylation and an O-allylation followed by Claisen rearrangement. The conjugation of the glycolipids to synthetic long peptides (p31-60 and p75-105 Rv2034, p57-84 Rv1733c) was performed via thiol-maleimide addition. These constructs are being tested using a model HEK293-hMincle system and human monocyte-derived dendritic cells to verify binding to Mincle and study IL-10 and IL-12 production.
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