## 2 Materials and Methods
### Chlorination Reaction
#### 2.2.3 Chlorination Procedure and Product Isolation  
Olmesartan acid (1 g, 2.24 mmol) was solubilized in 1.0 L of phosphate buffer (KH\({}_{2}\)PO\({}_{4}\)/K\({}_{2}\)HPO\({}_{4}\) 0.1 M) [26]. A sodium hypochlorite solution (about 6% active chlorine, molar ratio OLM/HCIO 1:20; concentration spectroscopically determined at \(\lambda_{\max}\) of 292 nm, \(\epsilon=350\) dm\({}^{3}\)/mol cm) was added drop by drop to this solution under magnetic stirring at room temperature. The phosphate buffer pH was adjusted to 6.50 by adding a 10% H\({}_{3}\)PO\({}_{4}\) solution, checking with a pH-meter. Reaction was stopped after 2 h with an excess of sodium thiosulfate and concentrated by lyophilization. The residue was dissolved in water, pH is adjusted to 7.00, and this solution was extracted with ethyl acetate. The aqueous solution was subsequently extracted with \(n\)-butanol (B). The crude EA fraction (579 mg) was chromatographed on silica gel CC, eluting with a gradient of methylene chloride:methanol:acetic acid (100:0.5 to 70:30:0.5, _v/v/v_) to yield sixteen fractions. The fraction EA1 (26 mg), eluted with methylene chloride:methanol:acetic acid (100:0.5, _v/v/v_), was separated by semipreparative HPLC using a reversed phase column Kromasil 10 \(\upmu\)m 100 A C18 (250 \(\times\) 10 mm) and eluting with a gradient of CH\({}_{3}\)COONH\({}_{4}\) (A, pH 4.0; 10 mM) and methanol (B), starting with 85% B for 1 min and using a gradient up to 100% B in 25 min, at a solvent flow rate of 2 mL/min, to yield DP10 and DP11 (3.1 and 1.3 mg, respectively). The fraction EA6 (76 mg), eluted with methylene chloride:methanol:acetic acid (95:5:0.5, _v/v/v_), was analyzed via preparative HPLC using a reversed-phase Gemini column of 10 \(\upmu\)m C18 110 A (250 \(\times\) 21 mm), eluting with a gradient of CH\({}_{3}\)COONH\({}_{4}\) (A, pH 4.0; 10 mM) and methanol (B), starting with 60% B for 1 min and using a gradient up to 100% B in 30 min at a solvent flow rate of 7.5 mL/min to get five subfractions. The subfraction EA6.1 (33 mg) was re-chromatographed by HPLC using a reversed-phase Kinetex column of 2.6 \(\upmu\)m 100 A C18 (100 \(\times\) 4.6 mm), eluting with a gradient of CH\({}_{3}\)COONH\({}_{4}\) (A, pH 4.0; 10 mM) and acetonitrile (B), starting with 40% B for 1 min and using a gradient up to 100% B in 30 min, at a solvent flow rate of 0.8 mL/min, to yield DP12, DP14, and DP17 (1.4, 1.1, and 13.4 mg, respectively). The subfraction EA6.2 (5 mg) was re-chromatographed by HPLC using a reversed-phase Kinetex column of 2.6 \(\upmu\)m 100 A C18 (100 \(\times\) 4.6 mm), eluting with a gradient of CH\({}_{3}\)COONH\({}_{4}\) (A, pH 4.0; 10 mM) and acetonitrile (B), starting with 50% B for 1 min and using a gradient up to 100% B in 30 min, at a solvent flow rate of 0.8 mL/min, to get DP15 (2.1 mg). The fraction EA10 (51 mg), eluted with methylene chloride:methanol:acetic acid (85:15:0.5, _v/v/v_), was analyzed by semipreparative HPLC using a reversed-phase Kromasil column of 10 \(\upmu\)m 100 A C18 (250 \(\times\) 10 mm) and eluting with a gradient of CH\({}_{3}\)COONH\({}_{4}\) (A, pH 4.0; 10 mM) and methanol (B), starting with 35% B for 1 min and using a gradient up to 100% B in 20 min, at a solvent flow rate of 4 mL/min, to yield four subfractions. The subfractions EA10.1 (7 mg) was re-chromatographed by HPLC using a reversed-phase Kinetex column of 2.6 \(\upmu\)m 100 A C18 (100 \(\times\) 4.6 mm) and eluting with a gradient of acetic acid:acetonitrile (A, 1:99, _v/v_) and acetic acid:water (B, 1:99, _v/v_), starting with 75% B for 3 min and installing a gradient to obtain 100% A over 35 min and returning to 75% B for 10 min, at a solvent flow rate of 0.8 mL/min. It contained DP13 (3.2 mg).