Comparison of phorbol 13-acetate, HMI-1a3, 2b and 1f docked into the PKC<i>δ</i>C1B domain (PDB: 1PTR).

<p>(A) Phorbol 13-acetate; (B) HMI-1a3; (C) <b>2b</b>; (D) <b>1f</b>. Color code: carbon atoms are shown in grey, oxygen atoms in red, nitrogen atoms in blue and fluorine atoms in lime. Hydrogen bonds are represented as cyan dashed lines. View from the top of the binding site.</p

Synthesis and derivatization of the 2,4,6-trisubstituted pyrimidines 1a–h.

<p>Conditions: (a) MeCN/1,4-dioxane, rt, 24 h, 63%; (b) alcohol, H₂SO₄ (cat.), 100 °C, 3 h, 17–84%; (c) CAN, MeCN/H₂O, -15 °C, 10 min, 49–80%.</p

Data comparison for HMI-1a3, symmetrical pyrimidines 1a–h and unsymmetrical pyrimidines 2a–l.

<p>Binding affinity of pyrimidine derivatives expressed as the mean + standard error of the mean (SEM) (n = 2–8) of residual [³H]PDBu binding (% of control) at 20 μM compound concentration. The raw data of the displacement assay is available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195668#pone.0195668.s002" target="_blank">S2 File</a>.</p

Synthesis and derivatization of the 2,4,5,6-tetrasubstituted pyrimidines 2a–l.

<p>Conditions: (a) TEA, EtOH, reflux, 2.5 h, 31%; (b) POBr₃, DMF, MW 90 °C, 10 min, 75%; (c) alcohol, NaH, THF, 0 °C → rt, overnight (20–22 h), 5–68%; (d) SOCl₂, alcohol, MW 90 °C, 1 h, 33–50%; (e) CDI, DBU, DMAP, DMF, MW 50 °C, 1 h, 51–74%; (f) 2 M Me₃SiCHN₂ in Et₂O, CH₂Cl₂/MeOH, 0 °C, 30 min, 44–100%; (g) CAN, MeCN/H₂O, -15 °C, 10 min, 17–76%.</p

Representative binding curves for HMI 1a3, pyrimidines 1e, 1g, 2d, 2l and PMA.

<p>Binding of [³H]PDBu (10 nM) to purified PKC<i>α</i> measured in the presence of increasing concentrations of the tested compounds. The data is presented as mean of residual [³H]PDBu binding (% of control) from three parallel samples in a single representative experiment. The raw data of the displacement assays are available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195668#pone.0195668.s002" target="_blank">S2 File</a>.</p

Scaffolds comparison.

<p>Comparison of the HMI scaffold (left) with the symmetrical 2,4,6-trisubstituted pyrimidine (center) and the asymmetrical 2,4,5,6-tetrasubstituted pyrimidine (right) scaffolds. Common moieties are color-coded: H-bond donor/acceptor hydroxy groups are shown in blue, carbonyl H-bond acceptor oxygens in red and hydrophobic substituents R in green.</p

3D chemographic plot of PKC-targeted compounds from two different angles.

<p>Color code: Pyrimidines are shown in green; HMIs in blue; bryostatins in red; phorbol esters in yellow; DAG-lactones in purple; iripallidal in black, ingenol 3-angelate and prostratin in orange; mezerein in cyan; 9-decyl-benzolactam-V8 and indolactam-V in magenta. Pyrimidines <b>1e</b> and <b>2a</b>, HMI-1a3 (towards the PC2-boundary) and HMI-1b11 (central area) are represented as cubes. The full list of the compounds, ChemGPS-NP raw data, SMILES and structures are available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195668#pone.0195668.s001" target="_blank">S1 File</a>.</p