Letters in Organic Chemistry, 2009, 6, 297-300
297
Effects of Ionic Liquids for Lipase-Catalyzed Chiral 1,1`-binaphthyl-2-
yl(phenyl)methanone O-acetyl Oxime Synthesis
Yongchang Zhou*,a,b, Motohiro Takahashia,b, Naoto Aoyagia, Chunlei Lia, Tatsuro Kijimaa and
Taeko Izumia
aChemistry and Chemical Engineering, Graduate School of science and engineering, Yamagata University, Jonan 4-3-
16, Yonezawa 992-8510, Japan
bTechnology Department, Yonezawa Hamari Chemicals, Ltd. Hachimanpara 2-4300-18, Yonezawa 992-1128, Japan
Received May 21, 2008: Revised March 17, 2009: Accepted March 26, 2009
Abstract: The resolution of 1,1'-binaphthyl-2-yl(phenyl)methanone O-acetyl oxime catalyzed by lipase in three different
ionic liquids, 1-butyl-3-methylimidazolium hexafluoride-phosphate, [bmim][PF6], 1-butyl-3-methylimidazolium tetra-
fluoroborate, [bmim][BF4] and N-butyl-pyridium hexafluorophosphate, [BuPy][PF6] and organic solvents was studied.
The lipase shows low activity in ionic liquids and organic solvent with ionic liquids as the additive, while the lipase
coated with ionic liquids gives the best enantioselectivity as high as 95 %
Keywords: Ionic liquids, Lipase-catalyzed, Chiral, O-acetyl oxime, Synthesis, Resolution.
INTRODUCTION
the application of ionic liquids on this reaction. Therefore, it
is necessary to study ionic liquids as alternative solvents for
biotransformations using lipase for synthesis of chiral oxime
1 and 2.
Room-temperature ionic liquids (RTILs) are known as
green solvents used as reaction media in the separation
process and electrochemistry and have attracted much
attention in recent years because of their negligible vapor
pressures. The application of ionic liquids on organic
synthesis has been well documented in the reviews.
Moreover, bio-catalysis in ionic liquids has also been
In this paper, the effect of ionic liquids on lipase-
catalyzed resolution of 1,1'-binaphthyl-2- yl(phenyl)meth-
anone O-acetyl oxime was examined.
Ph
Ph
lipase
Ph
+
N
N
N
OH
OAc
OAc
(Z)-(S)-1
(Z)-(R)-2
(Z)-(±)-1
Scheme 1. Lipase-catalyzed hydrolysis of (Z)-(±)-1
investigated in many chemical reactions, such as transesteri-
fication, synthesis, conversion, alcoholysis, ammoniolysis,
hydrolysis, epoxidation, resolution, oxidation, reduction,
deracemization etc. Unlike the conventional organic solv-
ents, the use of enzymes and substrates in ionic liquids can
enhance the activity, selectivity, and stability of catalysts [1-
11].
RESULTS AND DISCUSSION
We reported before that the optimal condition of enzyme-
resolution was carried out at 60 ˚C, so we wanted to find a
suitable ionic liquid, whose melting point is above 60 ˚C.
N-butyl-pyridium hexafluoride phosphate ([Bupy][PF6]) is
the suitable one since its melting point is 68 ˚C.
The successful approach involved the enzymatic resolu-
tion of (±)-1 under hydrolysis condition, using lipase prepa-
rations according to Scheme 1.
Lipase-catalyzed resolution of title compound has been
reported for the synthesis of chiral oxime, but the enatioex-
cess is not good enough [12]. No research was conducted on
In order to compare the effect of ionic liquids, we do the
lipase-catalyzed resolution with methyl tertiary-butyl ether
(MTBE) as a solvent only at the very beginning. As shown
in Table 1, entry 1, 36% yield is obtained for (Z)-(R)-2 and
83% yield for enatio-excess (ee) after 22 h reaction.
*Address correspondence to this author at the Technology Department,
Yonezawa Hamari Chemicals, Ltd. 2-4300-18, Hachimanpara, Yonezawa-
city 992-1128, Yamagata, Japan; Tel: +81-238-28-3809;
E-mail:yczhou97@hotmail.com
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© 2009 Bentham Science Publishers Ltd.