Pseudomonas sp. Lipases
Bacterial lipases isolated from Pseudomonas fluorescens, P. aeruginosa, P. cepacia,
and P. glumae are highly selective catalysts [469].
16 They seem to possess a
‘narrower’ active site than CRL, since they are often unable to accommodate bulky
substrates, but they can be extremely selective on ‘slim’ counterparts [470–474]. Like
the majority of the microbial lipases, the commercially available crude Pseudomonas
sp. lipase preparations (PSL) all possess a stereochemical preference for the hydrolysis of the (R)-esters of secondary alcohols, but the selectivity among the different
preparations may differ to some extent [475]. Various active-site models for PSL
have been proposed [179, 476–478] and the crystal structures of P. cepacia and
P. glumae lipases were elucidated by X-ray analysis [479, 480].
The exceptionally high selectivity of PSL on ‘narrow’ open-chain esters is
demonstrated by the following examples (Scheme 2.59).
The desymmetrization of some prochiral dithioacetal esters possessing up to five
bonds between the prochiral center and the ester carbonyl – the site of reaction –
proceeded with high selectivity using PSL [481]. This example of a highly selective
chiral recognition of a ‘remote’ chiral/prochiral center is not unusual amongst
hydrolytic enzymes [482–484].
Chirality need not reside on a sp
3 carbon atom to be recognized by PSL but can
be located on a sulfur atom (Scheme 2.60). Thus, optically pure aryl sulfoxides
were obtained by lipase-catalyzed resolution of methyl sulfinyl acetates [485] in a
biphasic medium containing toluene. The latter compounds are important starting
materials for the synthesis of chiral allylic alcohols via the ‘SPAC’ reaction.
Cl
N
Ar
CO 2 Me
MeO 2 C
Ar
CO 2 H
MeO 2 C
Ar =
buffer
Pseudomonas sp. lipase
*
* = Chirality center
( ) n
( ) n
( ) n
( ) n
n
1
2
3
Distance
a
3
4
5
e.e. [%]
48
>98
79
a Number of bonds between
prochiral center and ester group
*
Scheme 2.59 Desymmetrization of esters having a remote prochiral center by Pseudomonas
sp. lipase
16 Several Pseudomonas spp. were reclassified as Burkholderia spp.
96
2 Biocatalytic Applications
Bacterial lipases isolated from Pseudomonas fluorescens, P. aeruginosa, P. cepacia,
and P. glumae are highly selective catalysts [469].
16 They seem to possess a
‘narrower’ active site than CRL, since they are often unable to accommodate bulky
substrates, but they can be extremely selective on ‘slim’ counterparts [470–474]. Like
the majority of the microbial lipases, the commercially available crude Pseudomonas
sp. lipase preparations (PSL) all possess a stereochemical preference for the hydrolysis of the (R)-esters of secondary alcohols, but the selectivity among the different
preparations may differ to some extent [475]. Various active-site models for PSL
have been proposed [179, 476–478] and the crystal structures of P. cepacia and
P. glumae lipases were elucidated by X-ray analysis [479, 480].
The exceptionally high selectivity of PSL on ‘narrow’ open-chain esters is
demonstrated by the following examples (Scheme 2.59).
The desymmetrization of some prochiral dithioacetal esters possessing up to five
bonds between the prochiral center and the ester carbonyl – the site of reaction –
proceeded with high selectivity using PSL [481]. This example of a highly selective
chiral recognition of a ‘remote’ chiral/prochiral center is not unusual amongst
hydrolytic enzymes [482–484].
Chirality need not reside on a sp
3 carbon atom to be recognized by PSL but can
be located on a sulfur atom (Scheme 2.60). Thus, optically pure aryl sulfoxides
were obtained by lipase-catalyzed resolution of methyl sulfinyl acetates [485] in a
biphasic medium containing toluene. The latter compounds are important starting
materials for the synthesis of chiral allylic alcohols via the ‘SPAC’ reaction.
Cl
N
Ar
CO 2 Me
MeO 2 C
Ar
CO 2 H
MeO 2 C
Ar =
buffer
Pseudomonas sp. lipase
*
* = Chirality center
( ) n
( ) n
( ) n
( ) n
n
1
2
3
Distance
a
3
4
5
e.e. [%]
48
>98
79
a Number of bonds between
prochiral center and ester group
*
Scheme 2.59 Desymmetrization of esters having a remote prochiral center by Pseudomonas
sp. lipase
16 Several Pseudomonas spp. were reclassified as Burkholderia spp.
96
2 Biocatalytic Applications