34451-19-9Relevant articles and documents
The chiral pool as valuable natural source: New chiral mesogens made from lactic acid
Brombach,Neudoerfl,Blunk
scheme or table, p. 62 - 74 (2012/01/06)
Twenty new enantiopure chiral materials have been synthesized, showing liquid crystalline phases of smectic (SmA*), twisted grain boundary (TGB) and cholesteric (N*) type. The central ester-linkage as well as the length of the attached alkyl-chains were varied in a systematic way and the effects of these structural changes on the liquid crystalline properties have been studied. The liquid crystalline phases were characterized by means of differential scanning calorimetry, polarisation microscopy as well as small angle X-ray diffraction (SAXS). Copyright Taylor & Francis Group, LLC.
Highly enantioselective acylation of rac-alkyl lactates using Candida antarctica lipase B
Lee, Yeon Soo,Hong, Joo Hee,Jeon, Nan Young,Won, Keehoon,Kim, Bum Tae
, p. 948 - 951 (2013/09/03)
By using Candida antarctica lipase B under mild conditions, the highly enantioselective acylation of alkyl (R)-lactate from racemic mixture with vinyl alkanoate has been accomplished. In this research effects of the organic solvent, the alkyl chain length of the alkyl lactates and of the vinyl alkanoates, and the reaction temperature on the enantiomeric excess as well as the reaction rate, were investigated. In all cases, only alkyl (R)-lactate was stereoselectively acylated at >99.5% ee. The lipase-catalyzed acylation rate of the alkyl lactates was affected by the nature of the organic solvents, but showed no correlation to log P of the solvent. The lipase-catalyzed acylation rate of the alkyl lactates was enhanced by increasing the chain length of the vinyl alkanoate from acetyl to butanoyl and by raising the reaction temperature to 65°C. Finally, the lipase-catalyzed acylation and subsequent vacuum distillation successfully provided both butyl (R)-O-butanoyllactate and butyl (S)-lactate in excellent yields (48%) and enantioselectivities (>99.5% ee) on a large scale. It is expected that the present method will prove to be more efficient in achieving the chiral resolution of racemic alkyl lactate than other conventional methods in terms of environmental friendliness and simplicity.
Substrate Structure and Solvent Hydrophobicity Control Lipase Catalysis and Enantioselectivity in Organic Media
Parida, Sanghamitra,Dordick, Jonathan S.
, p. 2253 - 2259 (2007/10/02)
The lipase from Candida cylindracea catalyzes the enantioselective esterification of 2-hydroxy acids in nearly anhydrous organic solvents with primary alcohols as nucleophiles. The nature of the 2-hydroxy acid and organic reaction medium affects the efficiency of catalysis and the enantioselectivity. Straight-chain 2-hydroxy acids are highly reactive and give nearly 100% enantioselectivities in esterification reactions with 1-butanol. Slight branching with a methyl group adjacent to the 2-hydroxy moiety in toluene causes a substantial loss (up to 200-fold) in the lipase's catalytic efficiency with a concomitant loss in enantioselectivity. Losses in catalytic efficiency and enantioselectivity are also observed when the lipase is employed in hydrophilic organic media such as dioxane or tetrahydrofuran as compared to hydrophobic solvents such as toluene. With straight-chain substrates, the lipase is over 100-fold more active in toluene than in tetrahydrofuran or dioxane, while optimal enantioselectivity is observed in toluene. The loss in enantioselectivity in hydrophilic solvents is mainly due to a drop in the catalytic efficiencies of the S isomers, as the R isomers' catalytic efficiencies remain largely unchanged. In highly apolar solvents, such as cyclohexane, enantioselective relaxation occurs due to an increase in the reactivity of the R isomers relative to that of their S counterparts. These findings enabled a rational selection of substrates and solvents for a two-step, chemoenzymatic synthesis of optically active 1,2-diols to be carried out, the first step being the aforementioned enantioselective esterification of 2-hydroxy acids followed by reduction with LiAl(OCH3)3H to give the optically active 1,2-diol. Diols such as (S)-(+)-1,2-propanediol, (S)-(-)-1,2-butanediol, (S)-(-)-1,2-hexanediol, and (S)-(-)-4-methyl-1,2-pentanediol were produced in high optical purities (at least 98% enantiomeric excess (ee)).
