DL-Norleucine methyl ester hydrochloride

This study addresses in situ transesterification of highly wet microalgae with hydrochloric acid (HCl) as a catalyst. In situ transesterification was performed by heating the mixture of wet algal cells, HCl, methanol, and solvent in one pot, resulting in the fatty acid methyl ester (FAME) yield over 90% at 95°C. The effects of reaction variables of temperature, amounts of catalyst, reactant, and solvent, and type of solvents on the yield were investigated. Compared with the catalytic effect of H2SO4, in situ transesterification using HCl has benefits of being less affected by moisture levels that are as high as or above 80%, and requiring less amounts of catalyst and solvent. For an equimolar amount of catalyst, HCl showed 15wt.% higher FAME yield than H2SO4. This in situ transesterification using HCl as a catalyst would help to realize a feasible way to produce biodiesel from wet microalgae.

A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography-flame ionization detection, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs.

Isolation is the main bottleneck in the analysis of fatty acids in biological samples and foods. In the last few decades some methods described direct derivatization procedures bypassing these steps. They involve the utilization of methanolic HCL or BF3 as catalysts, but several evidences from previous works suggest these reagents are unstable, lead to the formation of artifacts and alter the distribution of specific compounds as hydroxy fatty acids or CLA. However, the main issue is that they are excellent esterification reagents but poor in transterification, being not suitable for the analysis of all lipid classes and leading to erroneous composition quantitations. The present research work is a comprehensive comparison of six general methylation protocols using base, acid or base/acid catalysts plus a proposed method in the analysis of total fatty acids in lipid standards mixtures, foodstuff and biological samples. The addition of aprotic solvents to the reaction mixture to avoid alterations was also tested.

In this study, a new method was developed to prepare enantiopure caffeic acid amides by enzyme-catalyzed asymmetric aminolysis reaction. Methoxymethyl chloride (MOMCl) was first introduced as a protective and esterified reagent to obtain the MOM-protected caffeic acid MOM ester 1d. Aminolysis reaction occurred between 1d and (R, S)-α-phenylethylamine in the presence of an immobilized lipase (Novozym 435) from Candida antarctica. Compared with the methyl-protected caffeic acid methyl ester 1c, 1d as substrate improved the lipase-catalyzed reaction rate by 5.5-fold. After Novozym 435-catalyzed aminolysis reaction was established, we evaluated the effects of synthesis parameters on the catalytic activity and enantioselectivity of Novozym 435. A reaction conversion rate of 25.5% and an E value of >100 were achieved under the following optimum conditions: reaction solvent, anhydrous isooctane; reaction temperature, 70°C; reaction time, 24h; ester-to-amine substrate molar ratio, 1:40; and enzyme additive amount, 40 mg.