Kinetic studies on lipase-catalyzed acetylation of 2-alkanol with vinyl acetate in organic solvent.
Lipase-catalyzed acetylation of 2-alkanol with vinyl acetate has been studied kinetically using Burkholderia cepacia lipase (BCL), enantiomerically pure (R)- and (S)-2-alkanols and different organic solvents. The rate equation was derived by the steady state method for the simplified mechanism. The second order rate constants (k(R) and k(S)) for (R)- and (S)-2-alkanols were evaluated from the slopes of the double reciprocal plots, v(-1) vs. [2-alkanol](-1), where v is the initial rate of the reaction. The log k(R) value increased with the solvent hydrophobicity log P, where P is a partition coefficient of a given solvent between octanol and water. The log k(S) value also increased with log P except the bulky solvents such as 1,4-dioxane and cyclohexane, in which the rates were faster than those expected from the log k(S) vs. log P plot. The slope of log k(S) vs. log P plot was larger than that for (R)-2-alkanol. Thus, log E (E=k(R)/k(S): enantioselectivity) decreased with log P except the bulky solvents. The rate constants and the enantioselectivity were different depending on the structure (carbon number CN) of 2-alkanol. The log E vs. CN plot was minimized at CN=8 and 10 and the log k(S) vs. CN plot maximized at CN=8 and 10. In contrast the log k(R) vs. CN plot showed a different feature from the log E vs. CN plot. These facts suggest that dependence of E on CN is more strongly affected by the reactivity of (S)-2-alkanol than that of (R) isomer in this acetylation.
Hirata
Hirofumi
H
Department of Bioscience and Technology, School of Engineering, Hokkaido Tokai University, Minami-ku, Sapporo, Japan. shinyatachibana@u01.gate01.com
Kawanishi
Mio
M
Iwata
Yusuke
Y
Sakaki
Keiji
K
Yanagishita
Hiroshi
H
D000107:Acetylation; D000438:Alcohols / Q000737:chemistry* / Q000378:metabolism*; D002384:Catalysis; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D015394:Molecular Structure; D012997:Solvents; D013237:Stereoisomerism; D013379:Substrate Specificity; D014753:Vinyl Compounds / Q000737:chemistry*
D000438:Alcohols; D012997:Solvents; D014753:Vinyl Compounds; D008049:Lipase; C011566:vinyl acetate