A series of N2,N4-disubstituted quinazoline-2,4-diamines has been synthesized and tested against multidrug resistant Staphylococcus aureus. A structure–activity and structure–property relationship study was conducted to identify new hit compounds. This study led to the identification of N2,N4-disubstituted quinazoline-2,4-diamines with minimum inhibitory concentrations (MICs) in the low micromolar range in addition to favorable physicochemical properties. Testing of biological activity revealed limited potential for resistance to these agents, low toxicity, and highly effective in vivo activity, even with low dosing regimens. Collectively, these characteristics make this compound series a suitable platform for future development of antibacterial agents.

A series of N2,N4-disubstituted quinazoline-2,4-diamines has been synthesized and tested against Leishmania donovani and L. amazonensis intracellular amastigotes. A structure–activity and structure–property relationship study was conducted in part using the Topliss operational scheme to identify new lead compounds. This study led to the identification of quinazolines with EC50 values in the single digit micromolar or high nanomolar range in addition to favorable physicochemical properties. Quinazoline 23 also displayed efficacy in a murine model of visceral leishmaniasis, reducing liver parasitemia by 37% when given by the intraperitoneal route at 15 mg kg–1 day–1 for 5 consecutive days. Their antileishmanial efficacy, ease of synthesis, and favorable physicochemical properties make the N2,N4-disubstituted quinazoline-2,4-diamine compound series a suitable platform for future development of antileishmanial agents.

A practical and efficient amidation reaction involving aromatic aldehydes and various azides under mild conditions is described. A broad spectrum of functional groups was tolerated, and the amides were synthesized in moderate to excellent yields, presenting an attractive alternative to the currently available synthetic methods.

ELQ-300, an investigational drug for treating and preventing malaria, shows potent transmission-blocking activity in rodent models of malaria.

Herein, we describe a practical, one-pot variant of the sulfo-click reaction, in which 9-fluorenylmethyl-protected thioesters are rapidly deprotected and reacted further with sulfonylazides to give N-acyl sulfonamides.

A library of 1,3-disubstituted 2-propanols was synthesized and evaluated as low molecular weight probes for β-secretase inhibition. By screening a library of 121 1,3-disubstituted 2-propanol derivatives, we identified few compounds inhibiting the enzyme at low micromolar concentrations. The initial hits were optimized to yield a potent BACE-1 inhibitor exhibiting an IC50 constant in the nanomolar range. Exploration of the pharmacological properties revealed that these small molecular inhibitors possessed a high selectivity over cathepsin D and desirable physicochemical properties beneficial to cross the blood–brain barrier.A library of 1,3-disubstituted 2-propanols was synthesized and tested as BACE-1 inhibitors. The compound with best activity was subjected to SAR studies to develop a nanomolar inhibitor with excellent selectivity over cathepsin D and predicted physicochemical properties optimal to penetrate BBB.

Antimalarial activity of 1,2,3,4-tetrahydroacridin-9(10H)-ones (THAs) has been known since the 1940s and has garnered more attention with the development of the acridinedione floxacrine (1) in the 1970s and analogues thereof such as WR 243251 (2a) in the 1990s. These compounds failed just prior to clinical development because of suboptimal activity, poor solubility, and rapid induction of parasite resistance. Moreover, detailed structure–activity relationship (SAR) studies of the THA core scaffold were lacking and SPR studies were nonexistent. To improve upon initial findings, several series of 1,2,3,4-tetrahydroacridin-9(10H)-ones were synthesized and tested in a systematic fashion, examining each compound for antimalarial activity, solubility, and permeability. Furthermore, a select set of compounds was chosen for microsomal stability testing to identify physicochemical liabilities of the THA scaffold. Several potent compounds (EC50 < 100 nM) were identified to be active against the clinically relevant isolates W2 and TM90-C2B while possessing good physicochemical properties and little to no cross-resistance.

ICI 56,780 (5) displayed causal prophylactic and blood schizonticidal activity (ED50 = 0.05 mg/kg) in rodent malaria models but produced rapid acquisition of parasitological resistance in P. berghei infected mice. Herein we describe the synthesis of analogues of 5 with EC50 as low as 0.15 nM against multidrug resistant P. falciparum. Optimal activity with low cross-resistance indexes (RI) to atovaquone was achieved by introducing ortho-substituted aryl moieties at the 3-position of the 7-(2-phenoxyethoxy)-4(1H)-quinolone core.

Kinetic target-guided synthesis (TGS) and in situ click chemistry are among unconventional discovery strategies having the potential to streamline the development of protein–protein interaction modulators (PPIMs). In kinetic TGS and in situ click chemistry, the target is directly involved in the assembly of its own potent, bidentate ligand from a pool of reactive fragments. Herein, we report the use and validation of kinetic TGS based on the sulfo-click reaction between thio acids and sulfonyl azides as a screening and synthesis platform for the identification of high-quality PPIMs. Starting from a randomly designed library consisting of 9 thio acids and 9 sulfonyl azides leading to 81 potential acylsulfonamides, the target protein, Bcl-XL, selectively assembled four PPIMs, acylsulfonamides SZ4TA2, SZ7TA2, SZ9TA1, and SZ9TA5, which have been shown to modulate Bcl-XL/BH3 interactions. To further investigate the Bcl-XL templation effect, control experiments were carried out using two mutants of Bcl-XL. In one mutant, phenylalanine Phe131 and aspartic acid Asp133, which are critical for the BH3 domain binding, were substituted by alanines, while arginine Arg139, a residue identified to play a crucial role in the binding of ABT-737, a BH3 mimetic, was replaced by an alanine in the other mutant. Incubation of these mutants with the reactive fragments and subsequent LC/MS-SIM analysis confirmed that these building block combinations yield the corresponding acylsulfonamides at the BH3 binding site, the actual “hot spot” of Bcl-XL. These results validate kinetic TGS using the sulfo-click reaction as a valuable tool for the straightforward identification of high-quality PPIMs.

Two fluorous diazirine photolabels were designed, synthesized and subjected to photoactivation studies. The photoactivation studies revealed an unexpected photoreaction when the fluorous tag was directly connected to the diazirine ring, leading to the formation of a fluorous alkene. The more efficient photolabel of the two was identified as a flexible precursor for target specific photoaffinity labels for fluorous proteomics by adding appropriate ligands depending on the target protein subset. As a proof of feasibility, mannose residues were added to the photolabel making it a potential photoaffinity label to tag proteins that bind mannose.

Since the 1940s endochin and analogues thereof were known to be causal prophylactic and potent erythrocytic stage agents in avian models. Preliminary screening in a current in vitro assay identified several 4(1H)-quinolones with nanomolar EC50 against erythrocytic stages of multidrug resistant W2 and TM90-C2B isolates of Plasmodium falciparum. Follow-up structure−activity relationship (SAR) studies on 4(1H)-quinolone analogues identified several key features for biological activity. Nevertheless, structure−property relationship (SPR) studies conducted in parallel revealed that 4(1H)-quinolone analogues are limited by poor solubilities and rapid microsomal degradations. To improve the overall efficacy, multiple 4(1H)-quinolone series with varying substituents on the benzenoid quinolone ring and/or the 3-position were synthesized and tested for in vitro antimalarial activity. Several structurally diverse 6-chloro-2-methyl-7-methoxy-4(1H)-quinolones with EC50 in the low nanomolar range against the clinically relevant isolates W2 and TM90-C2B were identified with improved physicochemical properties while maintaining little to no cross-resistance with atovaquone.

A divergent route was developed to access 3-iodo- and 6-chloro-3-iodo-4(1H)-quinolones for further elaboration via mono and/or sequential Suzuki−Miyaura cross-coupling to generate novel and medicinally important 4(1H)-quinolones. Copper- and palladium-catalyzed cyanations were used to functionalize the 4-quinolone core further.

Two fluorous diazirine photolabels were designed, synthesized and subjected to photoactivation studies. The photoactivation studies revealed an unexpected photoreaction when the fluorous tag was directly connected to the diazirine ring, leading to the formation of a fluorous alkene. The more efficient photolabel of the two was identified as a flexible precursor for target specific photoaffinity labels for fluorous proteomics by adding appropriate ligands depending on the target protein subset. As a proof of feasibility, mannose residues were added to the photolabel making it a potential photoaffinity label to tag proteins that bind mannose.

A practical and efficient amidation reaction involving aromatic aldehydes and various azides under mild conditions is described. A broad spectrum of functional groups was tolerated, and the amides were synthesized in moderate to excellent yields, presenting an attractive alternative to the currently available synthetic methods.

Herein, we describe a practical, one-pot variant of the sulfo-click reaction, in which 9-fluorenylmethyl-protected thioesters are rapidly deprotected and reacted further with sulfonylazides to give N-acyl sulfonamides.