## Materials and Methods
### Synthesis of Chalcones and Flavanones  
Synthesis of the compounds described below follows the general scheme outlined in 3.1 (Scheme 1). _2'-Hydroxy-4,4',6'-trimethoxychalcone_**1**. Compound **1** was synthesized by mixing 2'-hydroxy-4',6'-dimethoxyacetophenone (661.3 mg, 3.37 mmol) dissolved in a minimum (\(\sim\)15 mL) amount of tetrahydrofuran (THF) with sodium hydride (NaH) (2.5 equivalents), under nitrogen atmosphere at room temperature. After 30 min of stirring, 4-methoxybenzaldehyde (1.2 equivalents) was added to the reaction mixture and allowed to react for 3 h. The product was precipitated from the reaction  
Figure 1: Basic chalcone structure. mixture by pouring onto ground ice and acidifying to pH \(<\) 2 with HCl 37%. The solid was filtered and washed with water until pH \(>\) 5. The crude product was crystallized from ethanol and the desired compound **1** was obtained (928.1 mg, 88% yield). 2_\"-Hydroxy-4_,_4_',_6_'-trimethoxychalcone_**1**: yellow crystals (ethanol); m.p. 112.4-113.6 \({}^{\circ}\)C (Lit. 111-115\({}^{\circ}\)[31]). 1\({}^{\mathrm{\,}}\)H NMR (300 MHz, CDCl\({}_{3}\)) \(\delta\) 14.40 (1H, s, 2\({}^{\prime}\)-OH), 7.7  
was filtered to remove the K\({}_{2}\)CO\({}_{3}\) and washed with DMF. The filtrate was poured over crushed ice and HCl 20% added until pH \(<\) 5. The precipitated 4-benzylbenzylaldehyde was filtered and crystallized from ethanol (1.8 g, 78%). 2. The aldol condensation: The 2'-hydroxy-4',6'-dimethoxyacyacetophenone (898.3 mg) was dissolved in dried THF (\(\sim\)15 mL) and mixed with NaH (2.5 equivalents) at room temperature and under N\({}_{2}\) atmosphere. After 10 min, 4-benzylbenzylaldehyde (1.2 equivalents) was added, and the reaction was finished after 4 h by precipitation over crushed ice acidified with HCl 37% to pH \(<\) 2. 4-Benzyloxy-2'-hydroxy-4',6'-dimethoxyyachalcone **3** was obtained by crystallization from ethanol (1.433 g, 80%). 3. The benzyl group's cleavage: The chalcone **3** (330.6 mg) was mixed with 30 mL of a mixture of HCl/Acetic acid (1:10) under stirring at 55 \({}^{\circ}\)C during 60 h. The reaction was finished by pouring the mixture over crushed ice, the formed solid was washed with water until pH \(\sim\)5 and purified by TLC using hexane/ethyl acetate (1:1) as eluent, affording 4'-hydroxy-5,7-dimethoxyyflavanone **5** as pale-yellow amorphous powder (21.0 mg, 8%). 4'-_Hydroxy-5,7-dimethoxyyflavanone_**5**: 1\({}^{\mathrm{H}}\) NMR (300 MHz, CDCl\({}_{3}\)) \(\delta\) 7.29 (2H, d, \(J\) = 8.5 Hz, H-2', H-6'), 6.86 (2H, d, \(J\) = 8.5 Hz, H-3'and H-5'), 6.13 (1H, d, \(J\) = 2.3 Hz, H-8), 6.07 (1H, d, \(J\) = 2.3 Hz, H-6), 5.34 (1H, d, \(J\) = 3.0 and 12.8 Hz, H-2), 3.86 (3H, s, 5-OCH\({}_{3}\)), 3.81 (3H, s, 7-OCH\({}_{3}\)), 3.03 (1H, dd, \(J\) = 12.8 and 16.6 Hz, H-3a), 2.78 (1H, dd, \(J\) = 3.0 and 16.6 Hz, H-3b); 1\({}^{\mathrm{C}}\) NMR (75 MHz, CDCl\({}_{3}\)) \(\delta\) 190.2 (C-4), 166.2 (C-7), 165.2 (C-8a), 162.3 (C-5), 165.4 (C-4'), 130.4 (C-1'), 127.9 (C-2', C-6'), 115.7 (C-3', C-5'), 105.8 (C-4a), 93.6 (C-8), 93.1 (C-6), 78.9 (C-2), 56.1 (5-OCH\({}_{3}\)), 55.6 (7-OCH\({}_{3}\)), 45.2 (C-3); TOF-ESI-MS (+) _m/z_ 301 [M+H]\({}^{+}\), 323 [M+Na]\({}^{+}\), 623 [M+Na+M]\({}^{+}\). 2',4',4-Trilhydroxyxhalcone **6** and 4',7-dilhydroxyflavanone **7**. The 2',4'-dihydroxyacetophenone (226.7 mg) was dissolved in dried toluene and mixed with 10 mL of a 1 mol.dm\({}^{-3}\) solution of LiHMDS (6.6 equivalents), under nitrogen atmosphere, at room temperature. After 30 min, 4-hydroxybenzaldehyde (1.2 equivalents) was added, and the reaction was stirred for 5 days. The reaction was finished, poured over crushed ice and acidified to pH \(<\) 2 with HCl 37%. The mixture was extracted with CH\({}_{2}\)Cl\({}_{2}\) and purified by TLC, using a mixture of hexane and ethyl acetate (1:1) as eluent (twice). Compounds 2',4',4-trihydroxyxhalcone **6** and 4',7-dihydroxyflavanone **7** were obtained as yellow amorphous powder, respectively, 18.2 mg (5%) and 8.2 mg (2%). Approximately 80% of the starting acetophenone was also recuerated.