*3.6. X-ray Crystallography Studies on Compound 11*

Intensity data were collected with an Oxford Diffraction SuperNova CCD diffractometer using Cu-Kα radiation, the temperature during data collection was maintained at 100.0(1) using an Oxford Cryosystems cooling device. The structure was solved by direct methods and difference Fourier Synthesis [13]. Hydrogen atoms bound to the carbon atom were placed at their idealized positions using appropriate HFIX instructions in SHELXL, and included in subsequent refinement cycles. Hydrogen atoms attached to nitrogen were located from difference Fourier maps and refined freely with isotropic displacement parameters. Thermal ellipsoid plots were generated using the program ORTEP-3 [14] integrated within the WINGX suite of programs [15]. Full details of the data collection and refinement and tables of atomic coordinates, bond lengths and angles, and torsion angles have been deposited with the Cambridge Crystallographic Data Centre (CCDC 1416796). Copies can be obtained free of charge on application at the following address: http://www.ccdc.cam.ac.uk.

Crystal data for compound **11**: C17H14N2O6S2, *M* = 406.42, *T* = 100.0(2) K, λ = 1.5418 Å, Triclinic, space group *P21/c*, *a =* 11.6802(7), *b =* 28.0975(14), *c =* 10.3047(6) Å, β = 91.539(5)◦ *V =* 3380.6(3) Å3, *Z* = 8, *<sup>Z</sup>* = 2, *Dc* = 1.597 Mg·M−3, <sup>μ</sup> = 3.230 mm−1, *F(000)* = 1680, crystal size 0.49 mm × 0.38 mm × 0.31 mm. θmax = 67.6◦, 10,831 reflections measured, 5907 independent reflections (*R*int = 0.051) the final *R* = 0.0559 [I > 2σ(I), 5134 data] and *w*R(F2) = 0.1577 (all data) GOOF = 1.027.

#### *3.7. P. Falciparum Growth Inhibition Assay*

*P. falciparum* growth inhibition assays were carried out using an isotopic microtest, as previously described [16]. Briefly, *in vitro* cultured *P. falciparum* infected erythrocytes (1.0% parasitemia and 1.0% hematocrit) were seeded into triplicate wells of 96 well tissue culture plates containing vehicle control (DMSO), positive control [chloroquine (Sigma-Aldrich, St. Louis, MO, USA), catalogue #C6628, >98%] or test compounds and incubated under standard *P. falciparum* culture conditions with 0.5

μCi [3H]-hypoxanthine. The final concentration of DMSO vehicle was <0.5% in all assay wells (non-toxic). After 48 h cells were harvested onto 1450 MicroBeta filter mats (PerkinElmer, Waltham, Massachusetts, USA) and [3H] incorporation determined using a 1450 MicroBeta liquid scintillation counter. Percentage inhibition of growth compared to matched DMSO controls was determined and IC50 values were calculated using linear interpolation of inhibition curves [17]. The mean IC50 or % inhibition (±SD) was calculated for three independent experiments, each carried out in triplicate.
