Fine tuning Exo2, a small molecule inhibitor of secretion and retrograde trafficking pathways in mammalian cells.

The small molecule 4-hydroxy-3-methoxybenzaldehyde (5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidin-4-yl)hydrazone (Exo2) stimulates morphological changes at the mammalian Golgi and trans-Golgi network that are virtually indistinguishable from those induced by brefeldin A. Both brefeldin A and Exo2 protect cells from intoxication by Shiga(-like) toxins by acting on other targets that operate at the early endosome, but do so at the cost of high toxicity to target cells. The advantage of Exo2 is that it is much more amenable to chemical modification and here we report a range of Exo2 analogues produced by modifying the tetrahydrobenzothienopyrimidine core, the vanillin moiety and the hydrazone bond that links these two.

Simple oxidation of pyrimidinylhydrazones to triazolopyrimidines and their inhibition of Shiga toxin trafficking.

The oxidative cyclisation of a range of benzothieno[2,3-d]pyrimidine hydrazones (7a-j) to the 1,2,4-triazolo[4,3-c]pyrimidines (8a-j) catalysed by lithium iodide or to the 1,2,4-triazolo[1,5-c]pyrimidines (10a-j) with sodium carbonate is presented. A complementary synthesis of the 1,2,4-triazolo[1,5-c]pyrimidines starting from the amino imine 11 is also reported. The effect of these compounds on Shiga toxin (STx) trafficking in HeLa cells and comparison to the previously reported Exo2 is also detailed.