Controlled Lactonization of o-Coumaric Esters Mediated by Supramolecular Gels

Abstract

Fragrances are volatile organic compounds widely used in our daily life. Unfortunately, the high volatility required to reach human receptors reduces their persistency in the air. To contrast this effect, several strategies may be used. Among them, we present here the combination of two techniques: the microencapsulation in supramolecular gels and the use of profragrances. We report a study on the controlled lactonization of four esters derived from o-coumaric acid. The ester lactonization spontaneously occurs after exposure to solar light, releasing coumarin and the corresponding alcohol. To determine the rate of fragrance release, we compared the reaction in solution and in a supramolecular gel and we demonstrated that the lactonization reaction always occurs slower in the gel. We also studied the more suitable gel for this aim, by comparing the properties of two supramolecular gels obtained with the gelator Boc-L-DOPA(Bn)2-OH in a 1:1 ethanol/water mixture in different gelator concentration (0.2% and 1% w/v). The gel prepared with 1% w/v gelator concentration is stronger and less transparent than the other and was used for the profragrances encapsulation. In any case, we obtained a significative reduction of lactonization reaction in gel, compared with the same reaction in solution.

Experimental Correlation between Apparent pKa and Gelation Propensity in Amphiphilic Hydrogelators Derived from l-Dopa

“…Following this approach, in the past, we synthesized Boc-L-Dopa(Bn) 2 −OH on a multigram scale, using a known procedure. 13,14 This molecule demonstrated to be a robust and biocompatible 15 gelator that can be also used to trap different materials, such as calcium carbonate, 16 fragrances, 17,18 and antioxidants. 19 In this work, we aim to explore the possibility to prepare strong and reproducible hydrogels by modifying the Nprotecting group, replacing the Boc group with three saturated fatty acids, very common in nature: lauric acid (C12), palmitic acid (C16), and azelaic acid (C9).…”

“…The catechol unit of l -Dopa has a pivotal role in this approach because it may be functionalized by derivatization of the two hydroxyl groups, leading to the formation of more complex structures. Following this approach, in the past, we synthesized Boc- l -Dopa(Bn) 2 –OH on a multigram scale, using a known procedure. , This molecule demonstrated to be a robust and biocompatible gelator that can be also used to trap different materials, such as calcium carbonate, fragrances, , and antioxidants …”

Transparent Organogels as a Medium for the Light-Induced Conversion from Spiropyran to Merocyanine

“…Being composed of weak interactions, these fibres are usually easy to break and reform (reversible gels) [12,23], and the gel formation can be easily tuned [24]. For this reason, LMW gels are useful for several applications, as water decontamination [25][26][27][28][29][30], optical sensors [31,32], template synthesis (crystals, nanostructures) [33][34][35], cell growth [36,37], drug delivery, and release of compounds [38][39][40][41][42].…”

“…The solvent of these materials can, in turn, be water for hydrogels, or an organic solvent for organogels [43][44][45][46], that can be formed through exposure to ultrasound sonication [11,26] optical sensors [31,32], template synthesis (crystals, nanostructures) [33][34][35], cell growth [36,37], drug delivery, and release of compounds [38][39][40][41][42].…”