Abstract
Mycolactone A/B (MycA/B) is reportedly the sole virulence factor of Mycobacterium ulcerans which causes the neglected tropical disease Buruli ulcer. This disease involves tissue destruction and suppression of local inflammation. Simmonds has recently discovered a mechanism of action which may encompass almost all effects and mechanisms reported to date; MycA/B inhibits protein translocation - the passage of newly-translated polypeptides across or into endoplasmic reticulum (ER) membranes. This is mediated through inhibition of the Sec61 translocon, an ER transmembrane pore which permits passage of polypeptide chains. It is hypothesized that binding of mycolactone to Sec61 could be inhibited, with a small molecule, without affecting natural translocation. Discovery of such a molecule requires the development of an assay to test the extent to which mycolactone is binding to Sec61 and this is the aim of this project. It requires synthesis of a fluorophore-conjugated version of MycA/B.
The shortest published synthesis of MycA/B to date requires at least 19 steps for the core, 18 for the fatty acid tail and 2-3 more for their coupling and deprotection. Taking into consideration the slow and hazardous growth of M. ulcerans impeding isolation of MycA/B, it is currently not available in sufficient quantities for a feasible study of the proposed bioassay. In order to solve this problem, a novel semi-synthesis of MycA/B must be developed, and this must be amenable to conjugation with a fluorophore for use in a bioassay. In this work, efforts towards the novel synthesis of MycA/B pentaenoate side chain and eventually the semi-synthesis of MycA/B are reported.