Mol Biochem Parasitol. key phases of the parasite life cycle and in the blood stage, inhibiting infections in poultry9 (Figure 1). Both of these compounds showed low nanomolar potencies in a biochemical assay against cell viability assay, the hypoxanthine incorporation assay (HXI).10 Open in a separate window Figure 1 Structure and data of compounds of 1 MUC1 1 (data unpublished) and 210. This paper is focused on the monocyclic compound 1, containing a pyrrole and an unflanked 4-pyridyl, both considered undesirable motifs for further SAR development. Furthermore, poor Zinc Protoporphyrin kinase selectivity was seen with 1, as it also showed potent activity against several other human kinases. Due to these unfavourable properties of 1 1, an alternative core was sought for further analogue development with the aim of enhancing anti-parasitical activity against data of thiazole 3. Compound 3, when tested, showed similar biochemical potency and a slight drop in cellular potency when compared to compounds (1) and (2) (Figure 2), which Zinc Protoporphyrin was seen as a positive result for the changed thiazole core. To optimize the potency, we first examined the pendent 2-aminopyrimidine (Scheme 1). Open in a separate window Scheme 1 Reagents and conditions (a) LiHMDS (1M in THF), THF, 0 Zinc Protoporphyrin C to r.t., 25%; (b) (i) (Me)3SiCl, (nBu)4NBr, DMSO, THF, 0 C to r.t., (ii) tert-butyl 4-carbamothioyl-piperidine-1-carboxylate, EtOH, reflux, 79%; (c) (i) 4M HCl/dioxane (ii) HCHO, Na(OAc)3BH, AcOH, CH2Cl2, 47%; (d) (i) H2O2, Na2WO4.2H2O, AcOH; (ii) NH4OAc, 130 C or AlkNH2, THF, 70 C or ArNH2, TFA, sBuOH, 130 C, 10-45%. Alkylation of 4 with benzoate 5 was achieved using LiHMDS to give ketone 6. This was then reacted with (Me)3SiCl and (nBu)4NBr to yield the -chloro ketone similar chemistry to intermediate 15. Compound 15 then underwent a double SMe oxidation to the bis-sulfone with hydrogen peroxide and catalytic sodium tungstate, followed by displacement of the (methylsulfonyl)pyrimidine by the requisite amine. Open in a separate window Scheme 2 Reagents and conditions (a) LiHMDS (1M in THF), THF, 0 C to r.t., 80%; (b) (i) (Me)3SiCl, (nBu)4NBr, DMSO, THF, 0 C to r.t., (ii) tert-butyl 4-carbamothioylpiperidine-1-carboxylate, EtOH, reflux, 25%; (c) (i) 4M HCl/dioxane (ii) HCHO, Na(OAc)3BH, AcOH, CH2Cl2; (d) (i) H2O2, Na2WO4.2H2O, AcOH; (ii) NH4OAc, 130 C or AlkNH2, THF, 70 C or ArNH2, TFA, sBuOH, 130C,12-35% from (14) Replacement of the 4-fluoropenyl moiety with alkyl substituents gave rise to weakly active analogues (10, 11) which both showed a significant drop in biochemical potency when compared to 9c. The lower activity seen with the alkyl substituents could be attributed to their inability to sufficiently fill the hydrophobic pocket between the catalytic lysine (K570) and the small gatekeeper residue (T618) (Figure 3). Despite the binding potency of 11, it showed similar cellular potency to 9c, possibly resulting from poor kinase selectivity as 11 is capable of binding to kinases in the cell with larger gatekeepers.14 Introduction of the sulfone (16a) gave a compound with comparable IC50 values to 9c, but with a much improved kinase selectivity profile (Figure 5). To further enhance the kinase selectivity Zinc Protoporphyrin of the compounds, additional analogues were made with groups of greater polarity in an attempt to capitalize on additional interactions with the ADME assays (Table 4). Data for 9c showed a very good overall profile, good logD and stability along with good PAMPA and kinetic solubility. Despite an otherwise excellent profile, the LogD of 16a.