A computacional approach to the photochemical properties of 33'-hydroxy-3-arylpropenoic acid (3-hydroxycinnamic acid).

G. DE PIANO, ; M. L. SALUM, ; T. SCHMIDT DE LEÓN, ; F. J. LUQUE, ; P. ARROYO MÁÑEZ; ROSA ERRA BALSELLS

Castellón de la Plana, Valencia, Espana,

Congreso; Espa 2016, 10th Congress on Electronic Structure. Principle and applications.; 2016

Univesidad de Valencia-Sociedad de Fisico-Quimica Espanola

 Cinnamicacid derivatives in both E and Z isomers are present in all kinds of plants,and hence in herbs and derived medicines, cosmetics and foods. In nature, thesecompounds act as antioxidant and growth regulators in plants, fungi, bacteriaand viruses, and their therapeutic and technological applications have increasedexponentially. For example, two members of the family, 3,5-dimetoxy-4-hydroxy-cinnamicand α-cyano-4-hydroxy-cinnamic acids, are used as MALDI-MSphotosensitizers for the polypeptide and protein analysis (proteomic). For thisreason, further understanding of the physicochemical properties is necessary. Becauseof their molecular structure cinnamic acids can exist in E- and Z-forms, but onlythe E-isomers are commercially available. So, very few studies over Z-cinnamicacids have been reported. A noveland successful method of synthesis of Z-cinnamic acids by photoisomerization usingcommercial E-cinnamic acids has been developed by Dr.Erra-Balsells´ group1.During the studies of photoisomerization of E-cinnamic acids in acetonitrile anoteworthy fact was observed: while E-3-hydroxycinnamic acid in thephotostationary point presents an E/Z ratio of 32:68, in presence of base (amine),forming an ionic liquid (IL), this ratio falls to 18/82. This behaviour is onlyobserved in presence of hydroxyl group, but not with other substituents likemethoxy. Furthermore, the meta position seems to be necessary. Aprevious combined spectroscopic and computational study by our group aboutcinnamic acids in solution was highly useful to understand the structure of Z-isomersin polar solvents2. The results showed up the importance of the lossof planarity in the carboxylic sidechain. In thecase of the 3-hydroxycinnamic acids, the resultant structure favours theinteraction between the amine and both polar groups of the acid inducing anextra stabilization that prevents isomerization like in other cinnamic acids. References1.   M. L. Salum, C. J. Robles, R. Erra-Balsells. Org.Lett. 2010, 12, 4808-4811.2.   M. L. Salum, P. Arroyo Mañez, F. J. Luque, R.Erra-Balsells. J.Photochem. Photobiol. B: Biol. 2015, 148, 128-135.