ChemComm
Communication
all materials using free enzymes or enzymes immobilised nano- used as a support for the immobilisation of two different lipase
particles. Free PFL performed a complete conversion (100 mmol enzymes via recently reported12 TPRE method. The materials
of reactant per mg of enzyme) of reactant to products after 24 h have been tested for one step formation of pharmaceutically
of reaction whereas PFL immobilized (physically or chemically) important optimal isomers 4-(R)-hydroxycyclopent-2-en-1-(S)-
nanoparticles performed
a partial conversion. Physically acetate and 4-(S)-hydroxycyclopent-2-en-1-(R)-acetate by enzy-
adsorbed PFL materials performed around 78% conversion of matic hydrolysis of meso-cyclopent-2-en-1,4-diacetate. It is
reactant (78 mmol of reactant per mg of enzyme) whereas important to mention that enzyme PFL produced an optically
chemically immobilized PFL materials performed around pure enantiomer 4-(R)-hydroxycyclopent-2-en-1-(S)-acetate
60% conversion of reactant (60 mmol of reactant per mg of whereas CRL produced both optical isomers (see Table S2 in
enzyme). It is important to mention that free PFL or PFL ESI† for enatiomeric excess value). Hence the combination of a
immobilized (physically or chemically) nanoparticles produced suitable enzyme and a suitable superparamagnetic support can
only 4-(R)-hydroxycyclopent-2-en-1-(S)-acetate (2a of Scheme 1) be an important step for the industrial production of pharma-
without the formation of 4-(S)-hydroxycyclopent-2-en-1-(R)- ceutically important optical isomers with a single step separa-
acetate (2b of Scheme 1). Increasing the reaction times from tion of expensive enzymes from the reaction mixture by an
1 to 24 h, the concentration of 4-(R)-hydroxycyclopent-2-en-1- external magnetic field.
(S)-acetate decreases and the concentration of unwanted
The authors thank to the Royal Society of Chemistry for
cyclopent-2-en-1,4-diol (see Scheme 1, product 1) increases small research funds (2010–2011 and 2011–2012) to carry out
due to the further hydrolysis of acetate group to alcohol group. the chiral reaction using a chiral column. MES thank to the
Physically adsorbed PFL nanoparticles performed better in University of Central Lancashire for partial support on her PhD
catalytic conversion of reactant to desired product 4-(R)- scholarship.
hydroxycyclopent-2-en-1-(S)-acetate, however when re-used the
catalyst, the catalytic conversion reduced more than 50% in the
2nd and 3rd cycles whereas chemically immobilized PFL exhi-
bited a stable catalytic activity. The higher catalytic activity of
Notes and references
1 G.-W. Xing, X.-W. Li, G.-L. Tian and Y.-H. Ye, Tetrahedron, 2000, 56,
physically adsorbed PFL in the 1st cycle could be due to the
presence of free enzymes in the reaction mixture by partial
leaching from the nanoparticles.
3517–3522.
´
´
2 P. W. Tardioli, R. Fernandez-Lafuente, J. M. Guisan and
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When CRL (free and immobilised forms) was used as an
enzyme, both optical isomers were formed (see Fig. 3). The ratio
of 4-(R)-hydroxycyclopent-2-en-1-(S)-acetate to 4-(S)-hydroxy-
cyclopent-2-en-1-(R)-acetate in the product mixture was around
2 : 1. Free CRL exhibited the highest % conversion of reactant
whereas physically adsorbed CRL performed the lowest conver-
sion. In conclusion, CRL is catalytically less active compared to
PFL but suitable for the desymmetrisation of both acetoxy
groups of the reactant in an approximately 2 : 1 ratio.
The reactant meso-cyclopent-2-en-1,4-diacetate can forms a
tetrahedral intermediate complex with the catalytic triad of the
lipase active site (Asp/Glu-His-Ser)17 and the mono-acetoxy
products (see Scheme S1 in ESI†) are hydrolyzed from the active
site. The hydrolysed acetoxy group from the diacetoxy reactant
remains bound to the serine residue in the active site as an
acyl–enzyme intermediate complex. After the acyl–enzyme
intermediate is formed, water hydrolyses the acetoxy group,
forming acetic acid in the reaction mixture, which enables the
acid-catalysed hydrolysis of the mono-acetoxy product 2a to the
dihydroxy by-product 1 when the enzyme is PFL.
Chem., 1991, 1991, 195–200.
11 S. R. Ghorpade, R. K. Kharul, R. R. Joshi, U. R. Kalkote and
T. Ravindranathan, Tetrahedron: Asymmetry, 1999, 10, 891–899.
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16 B. Hodgson, Peer-reviewed PhD thesis, University of Central Lancashire,
Preston, UK, 2014.
17 S. Raza, L. Fransson and K. Hult, Protein Sci., 2001, 10, 329–338.
In summary, high surface area novel mesoporous core–shell
superparamagnetic nanoparticles have been fabricated and
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Chem. Commun., 2014, 50, 11185--11187 | 11187