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Relevant academic research and scientific papers

A variant of Yarrowia lipolytica lipase with improved activity and enantioselectivity for resolution of 2-bromo-arylacetic acid esters

A variant of Lip2p lipase from Yarrowia lipolytica yeast was used for the resolution of 2-bromophenyl and o-tolyl acid esters, an important class of chemical intermediates for the pharmaceutical industry. In comparison with wild-type Lip2p, this variant, which contains one single amino acid change in the active site of the enzyme, V232A, displayed an enantioselectivity enhanced by one order of magnitude for the resolution of 2-bromo-phenylacetic acid ethyl ester (E-value increased from 5.5 to 59 for wild-type and V232A, respectively) and by fourfold for the resolution of 2-bromo-o-tolylacetic acid ethyl ester (going from an E-value of 27 to 111 for the wild-type and V232A, respectively). A remarkable increase in reaction velocity was also observed for both compounds, as a result of a significant gain in reactivity towards the favoured (S)-enantiomer (3- and 16-fold increase for 2-bromo-phenylacetic and -o-tolylacetic acid ethyl esters, respectively). These results demonstrate the key role of the V232 amino acid in enantiomer recognition and selectivity.

Enantiodiscrimination of racemic electrophiles by diketopiperazine enolates: asymmetric synthesis of methyl 2-amino-3-aryl-butanoates and 3-methyl-aspartates

Enolates of (S)-N,N′-bis-(p-methoxybenzyl)-3-iso-propylpiperazine-2,5-dione exhibit high levels of enantiodiscrimination in alkylations with (RS)-1-aryl-1-bromoethanes and (RS)-2-bromoesters, affording substituted diketopiperazines containing two new stereogenic centres in high de. Deprotection and hydrolysis of the resultant substituted diketopiperazines provides a route to the asymmetric synthesis of homochiral methyl 2-amino-3-aryl-butanoates and 3-methyl-aspartates in high de and ee.

New efficient lipase from Yarrowia lipolytica for the resolution of 2-bromo-arylacetic acid esters

A new extracellular lipase (Lip2p) from the yeast Yarrowia lipolytica was used for the resolution of 2-bromo-arylacetic acid esters, an important class of chemical intermediates for the pharmaceutical industry. Its efficiency for the transesterification of racemic mixtures with 1-octanol in n-octane was compared with the most efficient lipases described to date, lipases from Burkholderia cepacia and Rhizomucor miehei. Resolution of 2-bromo-p-tolylacetic acid ethyl ester catalyzed by Y. lipolytica lipase showed an enantiopreference of 28, almost equal to that obtained with B. cepacia lipase (E = 30). Moreover, Y. lipolytica lipase presents a higher catalytic activity and an (S)-enantiopreference, while B. cepacia lipase is (R)-enantiomer selective. The most interesting result is that Y. lipolytica lipase has until now been the only enzyme able to catalyze the resolution of 2-bromo-o-tolylacetic acid ethyl ester (E = 27).

Lipase-catalyzed enantioselective transesterification toward esters of 2-bromo-tolylacetic acids

Lipases from Candida antarctica, Pseudomonas cepacia and Rhizomucor miehei were tested in the resolution of seven racemic substrates belonging to the (RS)-2-bromo tolyl acetate ester category, but differing either in the position of the methyl substituent on the acyl part of the aromatic ring, or in the structure of the alkyl group. Lipase-catalyzed kinetic resolution via transesterification reaction between the ester and octanol in octane revealed that, of the three enzymes tested, P. cepacia lipase is the most efficient for resolution of the various racemates, with R-enantiopreference. In addition, the position of the methyl substituent was found to play a key role in governing the enantioselectivity of the reaction. Using P. cepacia lipase and 2-bromo-m/p-tolyl- or 2-bromophenylacetic acid esters E-values of 6.

Towards a novel explanation of Pseudomonas cepacia lipase enantioselectivity via molecular modelling of the enantiomer trajectory into the active site

In the transesterification reaction between (RS)-2-bromophenyl acetic acid ethyl ester and 1-octanol in n-octane, Pseudomonas cepacia lipase enantioselectivity towards the (R)-isomer is 57. Two strategies are described to investigate the structural basis involved in this enzyme enantioselectivity. Molecular modelling of the tetrahedral intermediate mimicking the transition state enables the identification of two potentially productive substrate-binding modes for each enantiomer. However, the conformations obtained with the faster and slower-reacting enantiomers have equivalent potential energies and most of them possess the hydrogen bonds essential for catalysis. On this basis, it is not possible to distinguish the diastereomeric complexes. The second approach is original and consists in a simple but robust protocol of pseudomolecular dynamics simulations under constraints to map the probable trajectory of the enantiomers in the active site. Enzyme/substrate interaction energy is always found to be lower for the faster-reacting enantiomer, which satisfactorily corroborates the experimental results. Energy differences are attributed to specific interactions of these substrates with a network of hydrophobic residues lining the access path. Furthermore, mechanistic details suggest that the pivoting side chains of the hydrophobic residues act in a concerted step-tooth gear motion whose basic role is to select and guide the substrates towards the active site. With this type of lipase, such dynamic features could be the key explanation of this as yet unexplored enantiorecognition. For the slower-reacting enantiomer, it appears that the concerted motion of the side chains is perturbed when the substrate passes through a bottleneck formed by Val266 and Leu17. The enantioselectivity of mutant Val266Leu with a more bulky side chain at this position supports our assumption: by narrowing the bottleneck, the enantioselectivity was considerably enhanced as much as up to 200.