Síntese de derivados anfifílicos a partir do cardanol e aminoácidos: de fontes renováveis a novos híbridos moleculares bioativos

Abstract

Cashew nut shell liquid is a black, viscous and caustic oil extracted from the mesocarp of cashew nuts (Anacardium occidentale L.) and is very rich in long-chain alkylphenols and alkylresorcinols, such as anacardic acid and cardol. By means of industrial thermal processing carried out on the kernels, the fresh LCC is converted into technical LCC, with cardanol as the main component of the mixture, a 3-alk(en)ylphenol phenolic lipid where the side chain attached to aromatic ring can be pentadecyl, (Z)-pentadec-8-enyl, (8Z,11Z)- pentadeca-8,11-dienyl or (8Z,11Z,14Z)-pentadeca-8,11,14-trienyl. LCC is considered a byproduct of the cashew industry and is usually sold to companies abroad, that use it as raw material for production of polymers, paints, varnishes, and oils. In this sense, LCC has become a renewable and inexpensive source of functionalized organic substances as alternatives to petrochemicals, and is easily accessible in cashew-producing countries, where cardanol represents a versatile substrate for various molecular modifications aiming at numerous value-added substances, such as porphyrins, biosensors, markers, and fine chemicals. Motivated by promising results of in situ biological investigation of new cardanol-amino acid hybrids, this work aimed to synthesize such hybrids in order to evaluate the biological potentials of these yet-to-be-synthesized compounds. The cardanol mixture, isolated from technical LCC with good yield and purity, was subjected to oxidative cleavage with OsO4, where the 8-(3-hydroxyphenyl)octanoic acid was obtained as the product, which unfortunately could not be completely purified. An attempt was made to acetylate this acid to facilitate the purification, however, the 8-(3-hydroxyphenyl)octanoate methyl ester was obtained. In parallel, two amino acid esterification methods were studied, since the respective esters are necessary to synthesize the target hybrids. The Steglich method used in an attempt to synthesize L-phenylalanine methyl ester was unsuccessful. A second method of esterifying L-tyrosine with 2,2-dimethoxypropane was recently carried out, with the results proceeding as planned. Acetylation of the cardanol mixture occurred correspondingly and its side chain was oxidized, the acid product of which was coupled to the L-Tyrosine methyl esters, however, as idealized, the coupling between the L-Tyrosine methyl esters and the acid product 8-( 3- hydroxyphenyl)octanoic acid did not occur as expected.