ABSTRACT
This study deals with an experimental investigation into the trans-esterification behavior of two biocatalysts produced by different immobilization techniques of the same lipase from Pseudomonas cepacia. Biocatalysts catalyzed trans-esterification of commercial frying oil. It was verified that no enzyme leaching occurs and stepwise addition of ethanol is needed to improve the process performance. When stoichiometric ethanol has been added completely at the beginning of the reaction, percent mass fraction of esters reached 33% after 9 h and 52% after 30 h. Instead, when ethanol has been added in steps, ester production gradually increased at any time. Moreover, different amounts of biocatalyst were added to the reaction system and it was found that it is not necessary to add more than 3% of biocatalyst with respect to the oil mass to avoid inhibition. The immobilization method influences the reaction progress and the intermediate-glyceride profiles were analyzed. Results showed that the two biocatalysts have the same affinity towards triglycerides, but the covalently immobilized lipase (epobond P. cepacia) has a lower affinity towards diglycerides and monoglycerides and, in general, a lower activity than the absorbed lipase (lipo P. cepacia).
ABSTRACT
The addition of enantiopure sulfenic acids to oxoalkynes constitutes a new and efficient methodology for the synthesis of beta-sulfinyl alpha,beta-unsaturated carbonyl compounds. Sulfenic acids 3 and 4 were generated by thermolysis of suitable precursors and trapped in situ by oxoalkynes 5, affording (R(S),E)- and (S(S),E)-3-alkylsulfinyl-1-phenyl-2-propen-1-ones, 4-alkylsulfinyl-3-buten-2-ones, and 3-[(1S)-isoborneol-10-sulfinyl]-2-propenoates 6 and 7 in good yields and in enantiomerically pure form after simple column chromatography. (R(S),E)-3-[(1S)-isoborneol-10-sulfinyl]-1-phenyl-2-propen-1-one (6(R)a) was involved as a heterodiene in inverse-electron-demanding Diels-Alder reactions with readily available electron-rich dienophiles 14 and 15, corroborating in each case the sulfinyl auxiliary capability in controlling the stereochemical outcome of these cycloadditions. Furthermore, the addition of methylmagnesium iodide to the carbonyl moiety of 6(R)a demonstrated that the chiral sulfur atom exerts a remote stereocontrol in this reaction if assisted by the hydroxy group being part of the isoborneol substituent.
