Figure 1
From: Identification of New Shikonin Derivatives as Antitumor Agents Targeting STAT3 SH2 Domain

(A) Reported synthetic STAT3 inhibitors and SHK with lead compound. The analogous structure for these compounds is colored in red. (B) Synthesis of compounds PMM-158~PMM-173. Reagents and conditions: (a) concentrated sulfuric acid, ethanol, reflux, 24 h; (b) NH2NH2-H2O (85%), ethanol, reflux, 12 h; (c) (1) CS2/KOH, ethanol (95%), reflux, 24 h; (2) HCl, PH 5–6; (d) ClCH2COOH, ethanol, reflux, 12 h; (e) DCC, DMAP, CH2Cl2, 0 °C, 8 h.