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a
O
O
O
O
O
O
O
O
6-MeCL
S
5-MeCL
R
4-MeCL
S
3-MeCL
S
-selective
E
-selective
E
-selective
E
-selective
E
> 100
= 79
= 13
= 53
b
O
O
O
O
O
O
4-MeCL
S
4-EtCL
S
4-PrCL
S
-selective
E
-selective
E
-selective
E
= 17.6
= 12.4
= 4.6
c
O
O
O
O
O
O
O
O
6-MeCL
S
6-EtCL
S
6-PrCL
S
6-BuCL
S
-selective
E
-selective
E
-selective
E
-selective
E
= 12.0
= 4.8
= 2.8
= 4.1
d
O
O
O
O
O
O
O
O
O
O
O
O
3MePL
S -selective
5MeVL
non-selective
6MeCL
S -selective
7MeHL
R -selective
8MeOL
R -selective
12MeDDL
R -selective
Fig. 10
Enantiopreference of CALB-catalyzed ( a ) hydrolysis of methyl-substituted
ε
-caprolactones
[ 82 ], ( b ) hydrolysis of 4-alkyl-substituted
ε
-caprolactones [ 83 ], ( c ) transesterification of 6-alkyl-
substituted
ε
-caprolactones [ 84 ], and ( d ) transesterification of
ω
-methyl-substituted lactones [ 85 ]
Shioji et al. found a pronounced
(
S
)
-selectivity in the hydrolysis of 6-methyl-
ε
[ 82 ] .
Hydrolysis of CLs with substituents at different positions (Fig. 10 a ) showed that
there is an odd-even effect in the selectivity of CALB-catalyzed hydrolysis of
methyl-substituted CLs, and E was moderate to good. Similar odd-even effects have
been observed in the esterification of methyl-substituted decanoic acids when using
Candida rugosa lipase [ 77 ]. Peeters et al. studied the hydrolysis of 4-alkyl substi-
tuted CLs (Fig. 10 b ) employing Novozym 435 [ 83 ] . Increasing the substituent size at
the 4-position led to a rapid decrease of E from 17.6 to 4.6, although
-caprolactone (6-MeCL) employing CALB as the biocatalyst
(
E
>
100
)
(
S
)
-selectivity
was observed in all cases.
Transesterification reactions of substituted lactones were also studied. The
butanolysis of 6-MeCL evaluated by Bisht and coworkers in organic medium
employing CALB showed an
(
S
)
-preference, but with a significantly lower selec-
tivity
(
E
=
7
)
compared to the hydrolysis reaction [ 86 ] . van As et al. studied the
 
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