**Chalcones and Flavanones Bearing Hydroxyl and**/**or Methoxyl Groups: Synthesis and Biological Assessments**

**Gonçalo P. Rosa 1, Ana M. L. Seca 1,2, Maria do Carmo Barreto 1, Artur M. S. Silva 2 and Diana C. G. A. Pinto 2,\***


Received: 20 June 2019; Accepted: 14 July 2019; Published: 17 July 2019

**Abstract:** Chalcones and flavanones are isomeric structures and also classes of natural products, belonging to the flavonoid family. Moreover, their wide range of biological activities makes them key sca ffolds for the synthesis of new and more e fficient drugs. In this work, the synthesis of hydroxy and/or methoxychalcones was studied using less common bases, such as sodium hydride (NaH) and lithium bis(trimethylsilyl)amide (LiHMDS), in the aldol condensation. The results show that the use of NaH was more e ffective for the synthesis of 2-hydroxychalcone derivatives, while LiHMDS led to the synthesis of polyhydroxylated chalcones in a one-pot process. During this study, it was also possible to establish the conditions that favor their isomerization into flavanones, allowing at the same time the synthesis of hydroxy and/or methoxyflavanones. The chalcones and flavanones obtained were evaluated to disclose their antioxidant, anticholinesterasic, antibacterial and antitumor activities. <sup>2</sup>,4,4-Trihydroxychalcone was the most active compound in terms of antioxidant, anti-butyrylcholinesterase (IC50 26.55 ± 0.55 μg/mL, similar to control drug donepezil, IC50 28.94 ± 1.76 μg/mL) and antimicrobial activity. <sup>4</sup>,7-Dihydroxyflavanone presented dual inhibition, that is, the ability to inhibit both cholinesterases. 4-Hydroxy-5,7-dimethoxyflavanone and 2-hydroxy-4-methoxychalcone were the compounds with the best antitumor activity. The substitution pattern and the biological assay results allowed the establishment of some structure/activity relationships.

**Keywords:** chalcones; aldol condensation; biological activity; flavanones; cytotoxic; antioxidant; anticholinesterase
