*Article* **Synthesis of Lipophilic Esters of Tyrosol, Homovanillyl Alcohol and Hydroxytyrosol**

#### **Roberta Bernini \*, Isabella Carastro, Francesca Santoni and Mariangela Clemente**

Department of Agriculture and Forest Sciences (DAFNE), University of Tuscia, Via S. Camillo de Lellis, 01100 Viterbo, Italy; isabella109@alice.it (I.C.); santonifrancesca@yahoo.it (F.S.); marian.clem@unitus.it (M.C.)

**\*** Correspondence: roberta.bernini@unitus.it; Tel.: +39-0761-357-452

Received: 26 April 2019; Accepted: 10 June 2019; Published: 14 June 2019

**Abstract:** Low-molecular weight phenols such as tyrosol, homovanillyl alcohol and hydroxytyrosol are valuable compounds that exhibit a high number of health-promoting effects such as antioxidant, anti-inflammatory and anticancer activity. Despite these remarkable properties, their applications such as dietary supplements and stabilizers of foods and cosmetics in non-aqueous media are limited for the hydrophilic character. With the aim to overcome this limitation, the paper describes a simple and low-cost procedure for the synthesis of lipophilic esters of tyrosol, homovanillyl alcohol and hydroxytyrosol. The reactions were carried out under mild and green chemistry conditions, at room temperature, solubilizing the phenolic compounds in dimethyl carbonate, an eco-friendly solvent, and adding a little excess of the appropriate C2–C18 acyl chloride. The final products were isolated in good yields. Finally, according to the "circular economy" strategy, the procedure was applied to hydroxytyrosol-enriched extracts obtained by *Olea europaea* by-products to prepare a panel of lipophilic extracts that are useful for applications where solubility in lipid media is required.

**Keywords:** tyrosol; homovanillyl alcohol; hydroxytyrosol; dimethyl carbonate; lipophilic alkyl esters; hydroxytyrosol-enriched extracts; *Olea europaea*; green chemistry; circular economy
