5953-49-1Relevant academic research and scientific papers
Highly Focused Library-Based Engineering of Candida antarctica Lipase B with (S)-Selectivity Towards sec-Alcohols
Cen, Yixin,Li, Danyang,Xu, Jian,Wu, Qiongsi,Wu, Qi,Lin, Xianfu
supporting information, p. 126 - 134 (2018/12/05)
Candida antarctica lipase B (CALB) is one of the most extensively used biocatalysts in both academia and industry and exhibits remarkable (R)-enantioselectivity for various chiral sec-alcohols. Considering the significance of tailor-made stereoselectivity in organic synthesis, a discovery of enantiocomplementary lipase mutants with high (R)- and (S)-selectivity is valuable and highly desired. Herein, we report a highly efficient directed evolution strategy, using only 4 representative amino acids, namely, alanine (A), leucine (L), lysine (K), tryptophan (W) at each mutated site to create an extremely small library of CALB variants requiring notably less screening. The obtained best mutant with three mutations W104V/A281L/A282K displayed highly reversed (S)-selectivity towards a series of sec-alcohol with E values up to 115 (conv. 50%, ee 94%). Compared with the previously reported (S)-selective CALB variant, W104A, a single mutation provided less selectivity, while the synergistic effects of three mutations in the best variant endow better (S)-selectivity and a broader substrate scope than the W104A variant. Structural analysis and molecular dynamics simulation unveiled the source of reversed enantioselectivity. (Figure presented.).
Enzymatic kinetic resolution of aliphatic sec-alcohols by LipG9, a metagenomic lipase
Bandeira, Pamela T.,Alnoch, Robson C.,De Oliveira, Alfredo R.M.,De Souza, Emanuel M.,De O.P., Fábio,Krieger, Nadia,Piovan, Leandro
, p. 58 - 63 (2016/01/30)
Bioprospection for new enantioselective enzymes for application in organic synthesis is a prominent area of investigation in biocatalysis. In this context, here we present the evaluation of an immobilized lipase isolated from a metagenomic library (LipG9) for the enzymatic kinetic resolution (EKR) of aliphatic sec-alcohols, which are still challenging substrates, since low enantioselectivity values are usually observed for these resolutions. LipG9 was successfully employed in EKR of aliphatic alcohols, which were resolved with satisfactory conversions (19-59%) and enantiomeric excesses for alcohols (26-88%) and esters (30-96%) by transesterification reactions, demonstrating that its performance is equal to or better than commercially available enzymes for the same reaction.
Polystyrene-supported GaCl3: A new, highly efficient and recyclable heterogeneous Lewis acid catalyst for acetylation and benzoylation of alcohols and phenols
Rahmatpour, Ali
, p. 1048 - 1054 (2013/02/22)
A new, simple and highly chemoselective method for both acetylation and benzoylation of alcohols and phenols with acetic anhydride in the presence of polystyrene-supported gallium trichloride (PS/GaCl3) as a highly active and reusable heterogeneous Lewis acid catalyst is presented. In this catalytic system, primary, secondary and tertiary alcohols as well as phenols were converted to the corresponding acetates and benzoates with high yields. The heterogenized catalyst is of high reusability and stability in the acetylation reactions and was recovered several times with negligible loss in its activity or a negligible catalyst leaching, and also there is no need for regeneration. Remarkably, a selective mono-acetylation of symmetrical diols can be achieved chemoselectively by employing the same catalyst.
Novel sol-gel lipases by designed bioimprinting for continuous-flow kinetic resolutions
Hellner, Gabriella,Boros, Zoltan,Tomin, Anna,Poppe, Laszlo
supporting information; experimental part, p. 2481 - 2491 (2011/11/06)
The bioimprinting effect in sol-gel immobilization of lipases was studied to develop efficient novel immobilized biocatalysts with significantly improved properties for biotransformations in continuous-flow systems. The bioimprinting candidates were selected systematically among the substrate mimics already found in the active site of experimental lipase structures. Four lipases (Lipase AK, Lipase PS, CaLB and CrL) were immobilized by a sol-gel process with nine bioimprinting candidates using various combinations of tetraethoxysilane (TEOS), phenyltriethoxysilane (PhTEOS), octyltriethoxysilane (OcTEOS) and dimethyldiethylsilane (DMDEOS) as silica precursors. The biocatalytic properties of the immobilized lipases were characterized by enantiomer selective acylation of various racemic secondary alcohols in two different multisubstrate systems (mixture A: a series of alkan-2-ols rac-1a-e and mixture B: heptan-2-ol rac-1f and 1-phenylethanol rac-1g). Except with Lipase AK, the most significant activity enhancement was found with the imprinting molecules already found as substrate mimics in X-ray structures of various lipases. The synthetic usefulness of the best biocatalysts was demonstrated by the kinetic resolution of racemic 1-(thiophen-2-yl)ethanol (rac-1h) in batch and continuous-flow systems. Copyright
Hydroacetoxylation of olefins with acetic acid genetated in situ from vinyl acetate in the presence of ruthenium complexes
Khusnutdinov,Shchadneva,Khisamova,Dzhemilev
experimental part, p. 155 - 160 (2011/05/03)
Ruthenium complexes catalyze the decomposition of vinyl acetate releasing the acetic acid and its subsequent addition to linear and cyclic olefins.
Alkane reaction with a mixture of nitric acid and acetic anhydride
Svetlakov
, p. 1081 - 1084 (2007/10/03)
Alkanes C6-C10 at 15-20°C react with a mixture of concentrated HNO3 and acetic anhydride to afford nitrates of secondary alcohols in the yield up to 70%. Acetates of secondary alcohols, acetates and nitrates of β-nitroalcohols form in small quantity. Isooctane reacts under milder conditions to give a nitrate of β-nitroalcohol.
A NEW COMBINED OXIDIZING REAGENT SYSTEM, Fe(CH3CN)6(3+)-IO4(1-): OXIDATION OF PARAFFIN HYDROCARBONS
Kotani, Eiichi,Kobayashi, Shigeki,Ishii, Yoko,Tobinaga, Seisho
, p. 4680 - 4684 (2007/10/02)
Combined oxidizing reagent systems of Fe(AN)6ClO4)3 ( AN = acetonitrile ) with halogen oxyacids were investigated.In particular, reactions of paraffin hydrocarbons with a combined reagent system of Fe(AN)6(3+) were explored because of the high reactivity of this system in the oxidation of adamantane ( Table 1 ).Oxidation of bornane, norbornane, cyclohexane, and n-hexane gave the corresponding acetamides and acetates ( Tabla II ).These results shows that the title reagent system can efficiently oxidize organic substrates which have onset potentials of anodic current of ca. 2.7 V vs. saturated calomel electrode.Keywords - oxidation; paraffin hydrocarbon; combined reagent system; hexakisacetonitrile iron(III) perchlorate; halogen oxyacid; sodium periodate
Synthesis, Characterization, and Catalytic Activity of Beidellite-Montmorillonite Layered Silicates and their Pillared Analogues
Diddams, Paul A.,Thomas, John M.,Jones, William,Ballantine, James A.,Purnell, J. Howard
, p. 1340 - 1342 (2007/10/02)
A synthetic beidellite-smectite, characterized by a range of techniques, including high-resolution 27Al and 29Si solid-state n.m.r. spectroscopy, shows interesting catalytic activity (in secondary amine formation from cyclohexylamine, in ester production from hex-1-ene and acetic acid, and in ether synthesis from pentanol): the selectivities differ significantly from those of montmorillonite-smectites.
The Novel Synthesis of Alkyl Cyanides by the Reaction of Sodium Trialkylcyanoborate with Sodium Cyanide and Lead(IV) Acetate
Masuda, Yuzuru,Hoshi, Masayuki,Yamada, Tetsuo,Arase, Akira
, p. 398 - 399 (2007/10/02)
Sodium trialkylcyanoborates gave good yields of the corresponding alkyl cyanides in the reaction with sodium cyanide and lead(IV) acetate.
Acid-induced 13C Nuclear Magnetic Resonance Chemical Shift Changes of Ether and Ester Carbon Atoms
Begtrup, Mikael
, p. 1609 - 1618 (2007/10/02)
13C N.m.r. chemical shifts of ehters dissolved in tetrachloromethane are displaced on addition of trifluoroacetic acid.The displacements result from independent interactions of the acid with the substrate oxygen atoms and alkyl residues.The structure-dependent and stereoselective shift changes are useful for signal assignments, structure determination, conformational analysis, assessment of the distribution of rapidly interconverting conformers of esters, and estimation of the relative basicity of ethers.
