Multicomponent synthesis of 3-aminoimidazo[1,2-a]pyrimidines usually affords a product mixture containing varying amounts of the corresponding 2-amino regioisomer. Modified methods, particularly microwave heating, have been employed to suppress formation of this side-product, but none of the revised protocols are readily amenable to scale. A continuous flow adaptation was found to offer improved regioselectivity toward the targeted 3-amino regioisomer with significantly shorter reaction times and also widened the scope of the reaction to permit the use of aliphatic aldehyde building blocks.

A series of highly potent indole-3-glyoxylamide based antiprion agents was previously characterized, focusing on optimization of structure–activity relationship (SAR) at positions 1–3 of the indole system. New libraries interrogating the SAR at indole C-4 to C-7 now demonstrate that introducing electron-withdrawing substituents at C-6 may improve biological activity by up to an order of magnitude, and additionally confer higher metabolic stability. For the present screening libraries, both the degree of potency and trends in SAR were consistent across two cell line models of prion disease, and the large majority of compounds showed no evidence of toxic effects in zebrafish. The foregoing observations thus make the indole-3-glyoxylamides an attractive lead series for continuing development as potential therapeutic agents against prion disease.Highlights► Indole-3-glyoxylamides substituted at C-6 show markedly improved antiprion efficiency. ► Introducing substitution at positions 4, 5 or 7 was disfavored. ► Good correlation between activity in two cell line models of prion disease. ► C-6 substituted compounds had good metabolic stability and non-toxic in zebrafish.

Transmissible spongiform encephalopathies (TSEs) are a family of invariably fatal neurodegenerative disorders for which no effective curative therapy currently exists. We report here the synthesis of a library of indole-3-glyoxylamides and their evaluation as potential antiprion agents. A number of compounds demonstrated submicromolar activity in a cell line model of prion disease together with a defined structure−activity relationship, permitting the design of more potent compounds that effected clearance of scrapie in the low nanomolar range. Thus, the indole-3-glyoxylamides described herein constitute ideal candidates to progress to further development as potential therapeutics for the family of human prion disorders.

The conversion of cellular prion protein (PrPC) to the protease resistant isoform (PrPSc) is considered essential for the progression of transmissible spongiform encephalopathies (TSEs). A potential therapeutic strategy for preventing the accumulation of PrPSc is to stabilize PrPC through the direct binding of a small molecule to make conversion less energetically favourable. Using surface plasmon resonance (SPR)-based technology we have developed a procedure, based on direct binding, for the screening of small molecules against PrPC immobilized on a sensor chip. In this paper we report some problems associated with the immobilization of PrPC onto the sensor surface for conducting drug screening and how these problems were overcome. We demonstrated that the conformational change of PrPC on the chip surface leads to increased exposure of the C-terminal which was observed by the increase in quinacrine binding over time, and loss of heparin binding to the N-terminal. In addition, we also report the results of the successful screening of a library of 47 compounds of known activity in cell line or cell free conversion studies for direct binding to three forms of PrPC (huPrPC, t-huPrPC and moPrPC). These results show the usefulness of this technique for the identification of PrPC binding ligands and to gain some insight as to their potential mode of action.