Reaction Mechanism About Isomerization of Resin Acids and Synthesis of Acrylopimaric Acid Based on DFT Calculation

Acrylopimaric acid is considered one of the possible substitutes for petroleum-based polymeric monomers, which is an important industrial product. Resin acids were isomerized to form levopimaric acid(4), which reacted with acrylic acid to synthesize isomers of acrylopimaric acid. Density functional theory calculation was used to investigate the reaction mechanisms with seven reaction paths in five different solutions. The values of ΔG were sorted from highest to lowest by levopimaric acid(4), neoabietic acid(3), palustric acid(2), and bietic acid(1). From the perspective of dynamics, the energy barrier in the isomerization of palustric acid(2) to levopimaric acid(4) was the lowest, whereas the highest energy barrier was the isomerization of neoabietic acid(3) to levopimaric acid(4) in the same solution. The addition reaction of levopimaric acid(4) and acrylic acid(5) to acrylopimaric acid c(8) was the optimal reaction path dynamically. However, ΔG of acrylopimaric acid c(8) was higher than that of acrylopimaric acid d(9). In general, the rates of isomerization reactions for rosin resin acids and addition reaction for acrylopimaric acid in water were higher than those in other solvents. HOMO-LUMO and ESP were analyzed for 8 kinds of molecules. For acylpyimaric acid, the non-planar six-memed ring and the C-C double bonds were easily attacked by nucleophile, while the non-planar six-memed ring and the carboxyl group are easily reacted with electrophiles. The highest electrostatic potential of the eight molecules is located at H of the carboxyl group, while the highest electrostatic potential is located at C-O double bond of the carboxyl group.

ADDUCTS OF LEVOPIMARIC ACID WITH ACRYLIC ACID AND ETHANEDITHIOL AS ACID CORROSION INHIBITORS OF METALS

The adducts were synthesized by means of diene condensation reaction of levopimaric acid with acrylic acid, and through carrying out the free radical addition of ethandithiol to levopimaric acid. The composition and structure of these adducts were identified through data of the elemental analysis, IR and PMR spectroscopy. The efficiency of the synthesized diacids as corrosion inhibitors was determined by means of the gravimetric method (on mass losses of a sample of steel plate of mark C-3) in an acidic medium (solutions of 1H and 5H of sulfuric acid). The influence of the medium temperature and concentration of the used compounds on the degree of protection and corrosion inhibition coefficient was analyzed. It found that rise in temperature results in the increase of protective effect of the inhibitor. Note that the increase of the inhibitor concentration, raising the degree of protection though, is not so noticeable.

Novel C15 Triene Triazole, D-A Derivatives Anti-HepG2, and as HDAC2 Inhibitors: A Synergy Study

A series of novel C15 urushiol derivatives were designed by introducing a pechmann structure and F-, Cl-, and Br-nitro substituents with different electronic properties into its alkyl side chain, as well as a triazolyl functional group in its aromatic oxide. Their chemical structures were determined based on the analysis of the NMR (nuclear magnetic resonance) spectroscopic and mass spectrometric data. The results showed that compound 4 exhibited a strong inhibition of the HepG2 cell proliferation (half maximal inhibitory concentration (IC50): 2.833 μM to human hepatocellular carcinoma (HepG2), and 80.905 μM to human normal hepatocytes (LO2)). Furthermore, it had an excellent synergistic effect with levopimaric acid. The nitrogen atom of the triazole ring formed a hydrogen-bonding interaction with Gly103, Gly154, and Tyr308, which made compound 4 bind to histone deacetylase (HDAC)2 more tightly. One triazole ring and His33 formed a π–π stacking effect; the other, whose branches were deep into the pocket, further enhanced the interaction with HDAC2. Meanwhile, compound 4 involved a hydrophobic interaction with the residues Phe210 and Leu276. The hydrophobic interaction and π–π stacking provided powerful van der Waals forces for the compounds.