Lipase-Catalyzed Condensation Reaction of 4-Nitrobenzaldehyde with Acetyl Acetone in Aqueous–Organic Cosolvent Mixtures and in Nearly Anhydrous Media

The nature of the product(s) in lipase-catalyzed reaction of acetyl acetone with 4-nitrobenzaldehyde was found to depend upon the source of lipase and the reaction medium. Mucor javanicus lipase was found to give 70% aldol with 80% enantiomeric excess in anhydrous t-amyl alcohol. A 2:2 adduct was formed by the dimerization of the aldol along with an unsaturated cyclic ether as the side products in varying proportions depending upon the reaction medium and the lipase used.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Enzymatic Resolution of Ethyl α-Hydroxyphosphinates in a Modified Reaction Environment

The enzymatic resolutions of two racemic ethyl hydroxyalkane(P-phenyl)phosphinates were performed by both esterification and hydrolysis approaches. The first reaction was performed in anhydrous diisopropyl ether with triethylamine or pyridine as additives by using lipases from three different sources (Candida cylindracea, Aspergillus niger, and Mucor javanicus). The increase in enantioselectivity was observed when NEt₃ was applied. The second reaction—lipase-catalysed hydrolysis of ethyl butyryloxyalkane(P-phenyl)phosphinates—was carried out by Candida cylindracea lipase in diisopropyl ether saturated with water or in aqueous solutions containing MgCl₂, LiCl, or Triton X-100. The usefulness of biphasic systems consisting of diisopropyl ether and water or aqueous solution of MgCl₂, LiCl, or Triton X-100 also were tested. The use of biphasic system in the presence of Triton X-100 resulted in the higher conversion of the substrates.     

Cover Picture: Solid‐State Structural Characterization of Cutinase–ECE‐Pincer–Metal Hybrids (Chem. Eur. J. 17/2009)

The interfacial enzyme cutinase…? shown at the air–water interface on the cover, was site‐selectively modified with two different ECE‐pincer–metal complexes. The resulting cutinase–pincer–metal hybrids crystallized under halide‐rich conditions to give monomeric crystal structures, but also crystallized under halide‐poor conditions to form a metal‐induced dimer. See the Full Paper by R. J. M. Klein Gebbink, P. Gros, G. van Koten et al. on page 4270 ff. , for details of the chemistry and the crystal structures. Photograph: View from the island of Saba (Netherlands Antilles) taken by Birgit Wieczorek. Design: Birgit Wieczorek and Cornelis A. Kruithof.

     

Advances in Enzyme and Ionic Liquid Immobilization for Enhanced in MOFs for Biodiesel Production

Biodiesel is a promising candidate for sustainable and renewable energy and extensive research is being conducted worldwide to optimize its production process. The employed catalyst is an important parameter in biodiesel production. Metal–organic frameworks (MOFs), which are a set of highly porous materials comprising coordinated bonds between metals and organic ligands, have recently been proposed as catalysts. MOFs exhibit high tunability, possess high crystallinity and surface area, and their order can vary from the atomic to the microscale level. However, their catalytic sites are confined inside their porous structure, limiting their accessibility for biodiesel production. Modification of MOF structure by immobilizing enzymes or ionic liquids (ILs) could be a solution to this challenge and can lead to better performance and provide catalytic systems with higher activities. This review compiles the recent advances in catalytic transesterification for biodiesel production using enzymes or ILs. The available literature clearly indicates that MOFs are the most suitable immobilization supports, leading to higher biodiesel production without affecting the catalytic activity while increasing the catalyst stability and reusability in several cycles.     

Enantiomerically Pure Tribenzotriquinacenes through Stereoselective Synthesis

Inherently chiral acetophenones and benzaldehydes bearing the large, bowl‐shaped framework of tribenzotriquinacene (TBTQ) were synthesized in enantiomerically pure form employing enzyme catalysis. Five‐step sequences involving lipase CAL‐B lead to the (M)‐enantiomers, (+)‐2‐acetyl‐TBTQ (M)‐ 5 and (+)‐2‐formyl‐TBTQ (M)‐ 6 , whereas use of lipase PS leads to the (P)‐enantiomers, (?)‐2‐acetyl‐TBTQ (P)‐ 5 and (?)‐2‐formyl‐TBTQ (P)‐ 6 , with at least 99 % ee in each case. The absolute configuration of these rigid 3D building blocks was determined by X‐ray diffraction analysis of the ketones 5 and by comparison of their chiroptical properties with those of the aldehydes 6 .     

槐糖内酯的脂酶修饰

槐糖内酯是一种生物表面活性剂,槐糖内酯经脂酶修饰后,并未得到断裂内酯键的槐糖脂开环衍生物,而是有选择性地水解掉糖上的一个乙酰基。     

Enzymes of Opuntia ficus-indica (L.) Miller with potential industrial applications-I

We report on the screening of different enzymes such as arylamidases, lipases, proteinases, and glucosidases in plant extracts of the Cactaceae family, genus Opuntia, as well as on a newly purified plant proteases from O. ficus-indica fruit extracts. These proteinases showed the maximum activity at pH 5.2 and 55°C and FTC-casein was the best of the escreened substrates. Proteolytic activities were activated by anti-oxidant compounds and by some divalent cations. These proteinases were efficiently inhibited by cystein proteinase inhibitors and by 1,10-phenanth roline. The estimated M _t for the main proteolytic activity was about 23.2 kDa. The results on milk clotting characteristics suggest a potential use of the fruit cystein enzymes of this plant in dairy industries.     

Tuning Immobilized Commercial Lipase Preparations Features by Simple Treatment with Metallic Phosphate Salts

Four commercial immobilized lipases biocatalysts have been submitted to modifications with different metal (zinc, cobalt or copper) phosphates to check the effects of this modification on enzyme features. The lipase preparations were Lipozyme^®TL (TLL-IM) (lipase from Thermomyces lanuginose), Lipozyme^®435 (L435) (lipase B from Candida antarctica), Lipozyme^®RM (RML-IM), and LipuraSelect (LS-IM) (both from lipase from Rhizomucor miehei). The modifications greatly altered enzyme specificity, increasing the activity versus some substrates (e.g., TLL-IM modified with zinc phosphate in hydrolysis of triacetin) while decreasing the activity versus other substrates (the same preparation in activity versus R- or S- methyl mandelate). Enantiospecificity was also drastically altered after these modifications, e.g., LS-IM increased the activity versus the R isomer while decreasing the activity versus the S isomer when treated with copper phosphate. Regarding the enzyme stability, it was significantly improved using octyl-agarose-lipases. Using all these commercial biocatalysts, no significant positive effects were found; in fact, a decrease in enzyme stability was usually detected. The results point towards the possibility of a battery of biocatalysts, including many different metal phosphates and immobilization protocols, being a good opportunity to tune enzyme features, increasing the possibilities of having biocatalysts that may be suitable for a specific process.     

Rose Oxides: A Facile Chemo and Chemo‐Enzymatic Approach

Nonracemic rose oxides were synthesized from racemic or nonracemic monoterpene alcohol citronellol by a novel chemo and chemo‐enzymatic route. After the key step of bromomethoxylation of citronellol, the intermediate was dehydrobrominated by a base, followed by an acid catalyzed demethoxylation along with cyclization to furnish rose oxides in high yield. The racemic dehydrobrominated precursor was also kinetically resolved using various lipases to produce nonracemic rose oxides.