For the synthesis of 4-hydroxybutyl 3,4-dihydroxybenzoate (BDO-3,4DHB), 5 g of 3,4-DHB were introduced into a two-neck round bottom flask and dissolved in 10 molar equivalents of BDO, used as a reactive solvent. 5 % of PTSA was added to the solution, then stirred and heated to 100 °C under vacuum, for 24 h. The evolution of the reaction was monitored by 1 H NMR. After cooling to room temperature, the product was precipitated in cold water and recovered by filtration as a white crystalline solid. The synthesis of 2-hydroxyethyl 4-hydroxybenzoate (EG-4HB) was carried out in the same way, with 4-hydroxybenzoic acid (4-HB) and EG as the acid and the diol, respectively. 4hydroxybutyl 4-hydroxybenzoate (BDO-4HB), 6-hydroxyhexyl 4-hydroxybenzoate (HDO-4HB) and 2,3-dihydroxypropyl 4-hydroxybenzoate (glycerol-4HB) were also prepared with the same pathway, with BDO or HDO as diol, respectively, and glycerol as the triol.