Search

The beneficial effects of smoke and its constituents, karrikinolide (KAR1) and cyanohydrin glyceronitrile, on the germination of Mediterranean lowland species are well‐documented. However, very little is known about the role of these signals on the germination of plants at higher altitudes. In addition, lignin‐derived chemicals, such as syringaldehyde (SAL), have recently been proposed as overlooked cues for smoke‐induced germination. To address these gaps in the literature, we investigated the effects of smoke‐water and SAL on the germination of 10 midland species growing on serpentine soils. We also sought to determine whether SAL interacts with KAR1 and/or mandelonitrile (MAN, a cyanohydrin) to enhance seed germination. The results show that smoke‐water significantly improved the germination of three species (Barbarea duralii, Digitalis cariensis and Turritis laxa). SAL, on the other hand, had no positive effect on the germination of the 10 species tested. Furthermore, three smoke‐sensitive species and Verbascum cariense responded to KAR1 and/or MAN. Finally, SAL did not exert any synergistic effects on germination in interaction with KAR1 and MAN. In conclusion, we provide evidence that smoke is an important germination cue also for Mediterranean midland species. Moreover, SAL did not play a role in stimulating germination in smoke‐sensitive species, either independently or in combination with other smoke chemicals. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Institute of Science & Technology / Iğdır Üniversitesi Fen Bilimleri Enstitüsü Dergisi is the property of Igdir University, Institute of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The HNL from the defatted meal of the seeds of Pouteria sapota (PsHNL) was extracted with water, and the aqueous extract was immobilized over celite or lyophilized and used as semi-purified PsHNL. The aqueous extract was mixed with celite, ratios 1:1, 1:2 and 1:4, and lyophilized. The immobilized PsHNLdir-celite catalysed the addition of HCN to 1b in buffer saturated-DIPE (microaqueous system) with high enantioselectivity in the first cycle but diminished in the next two cycles, best results were obtained with the ratio 1:4. The reaction with PsHNLdir-celite in biphasic medium (5% citrates buffer) improved the conversion compared with the microaqueous system, but it was still lower to that obtained with the PsHNL. Other way of immobilization studied was the precipitation of the enzyme with acetone and immobilization on celite, the PsHNLpp-celite catalysed the enantioselective addition of HCN to 2-fluoro (1a), 2-chloro (1b), 2-bromo (1c), 2-methyl (1d) and 2-nitro (1e) benzaldehydes, in the biphasic medium (1:4 ratio, 5% citrates buffer). The enantiomeric excess (ee) of (R)-2a, (R)-2b, (R)-2c and (R)-2d were >98% and remained during the three cycles. The ee of 2-nitromandelonitrile was 82% and was raised to 95% in the third cycle. Compared with the PsHNL, the conversion of 1a and 1b diminished 6% and 40%, respectively, after third cycle; for 2c, conversion was almost 10% higher in the first two cycles and diminished 19% in the third; for 2d and 2e the conversion was between 18–13% and 31–18% higher, respectively. [ABSTRACT FROM AUTHOR]

The generation of the quaternary stereocenter at the C9 position of salvinorin A precursors by the Claisen rearrangement was investigated. The required allyl alcohol was prepared from a Wieland‐Miescher ketone using a known γ‐hydroxylation, reduction of the enone double bond, cyanohydrin formation, and elimination, yielding an unsaturated nitrile. A two‐step reduction led to the required allyl alcohol. The subsequent Johnson‐Claisen rearrangement provided a mixture of two diastereomeric 1,4‐unsaturated esters in a ratio of around 2.6 : 1. The major isomer could be converted to a key intermediate of the Hagiwara synthesis of salvinorin A. [ABSTRACT FROM AUTHOR]

A variety of cyanohydrin carbonates were readily prepared by the reaction of aldehydes with cyanoformate under the influence of γ-alumina using a convenient one-pot procedure. [ABSTRACT FROM AUTHOR]

The review focuses on the iron‐catalyzed cyanation reaction. This is the first review on this topic and covers literature till 2020 and comprehends all the works published in this field detailing the scope and limitations. The cyano compounds are important organic moiety and are widely used in synthetic organic chemistry; this review aims to help understand the various aspects of Fe‐catalyzed cyanation reactions and its scope. [ABSTRACT FROM AUTHOR]

Quaternary stereocenters are privileged structural motifs, widely distributed in natural products and in pharmaceutically active compounds. Asymmetric methods for the efficient construction of these prominent frameworks are rapidly increasing. Biocatalysis represents an alternative to the existing methods of using hazardous metals and chemicals. Enzymes discussed in this mini‐review involve thiamine‐bisphosphate (ThDP)‐dependent lyases, aldolases and hydroxynitrile lyases. The chiral products, (α‐alkyl‐α‐hydroxy ketones, α‐alkyl‐α‐hydroxy‐β‐diketones, β‐hydroxy ketones, ketone cyanohydrins) obtained by these enzymes, are valuable intermediates suitable for further transformations affording a variety of multi‐functionalized useful building blocks bearing a tetrasubstituted stereocenter, such as amino alcohols, diols, α‐hydroxy carboxylic acids, β‐hydroxy‐α‐amino acids to cite only a few. [ABSTRACT FROM AUTHOR]

Supported Ionic Liquid‐Like Phases have been found to be efficient organocatalysts for the synthesis of cyanohydrin esters under solvent‐free conditions by an "electrophile‐nucleophile dual activation" based on hydrogen bond formation. The combination of multiple and consecutive multicatalytic steps in a single and integrated cascade process of organocatalytic SILLPs with commercially available supported Candida antarctica lipase type B (CAL‐B) has allowed developing an efficient process for the multicatalytic synthesis of enantiopure cyanohydrins under flow conditions. Step it up: An integrated cascade multicatalytic multiple step flow process based on the appropriated combination of organocatalytic supported ionic liquid‐like phases (SILLPs) together with commercially available supported Candida antarctica lipase type B (CAL‐B) is reported for the efficient synthesis of enantiopure cyanohydrins. [ABSTRACT FROM AUTHOR]

We report the first application of Layered Double Hydroxides (LDHs) as efficient and novel heterogeneous catalyst for the cyanosilylation of aldehydes with excellent yields and simple work up. The reaction between different aldehydes with electron-withdrawing and releasing groups and trimethylsilyl cyanide (TMSCN) proceeds in dry CH2Cl2 at room temperature in the presence of Mg-Al-Cu LDH. The catalyst recycled and reused for four times without loss of catalytic activity. The structures of all compounds were corroborated spectroscopically (1H- and 13C-NMR, and elemental analysis). A plausible mechanism for this type of reaction is proposed. [ABSTRACT FROM AUTHOR]

Fermentation is one ways to reduce cyanogenic compounds in cassava. Fermentation of cassava is usually performed by submerged fermentation and solid state fermentation separately. "Gadungan pohung" is one of Indonesian traditional of cassava fermentations that combines spontaneous submerged and solid state fermentation simultantly. The objective of this study was to evaluate some chemical compound changes, microbiological profile, and cyanides reduction of three high cyanide cassava varieties during 3 days submerged fermentation and 3 days solid state fermentation simultaneously, in "gadungan pohung" processing. The resuls showed that submerged and solid state fermentation decreased most of nutritonal compounds of cassava except carbohydrate. Submerged fermentation reduced pH value from 6 to 4.5, meanwhile solid state fermentation increased pH value from 4.5 to 6. All cassava varieties revealed similar changes. Bacteria, mainly lactic acid bacteria, dominated during submerged and solid state fermentation. Yeasts were also found in higher number than molds. Cassava varieties slightly affected the pattern of microbial growth during solid state fermentation. Submerged fermentation reduced cyanide compounds. Some cyanide compounds were found in fermenting medium. Significant declined was found in cyanogenic glycosides, meanwhile cyanohydrin and free HCN increased in all cassava varieties. Solid state fermentation decreased cyanogenic glycosides and cyanohydrin, meanwhile concentration of free HCN were fluctuated during 3 days fermentation. Degradation of cyanides in solid state fermentation was due to microbial activity and increasing pH to above 5. Combination of submerged and solid state fermentation effectively reduced cyanide compounds in high cyanide cassava varieties to about 89-93%. [ABSTRACT FROM AUTHOR]

Ruthenium-catalyzed dehydrogenation of cyanohydrins under acceptorless and base-free conditions was demonstrated for the first time in the synthesis of acyl cyanide. As opposed to the thermodynamically preferred elimination of hydrogen cyanide, the dehydrogenation of cyanohydrins could be kinetically controlled with ruthenium (II) bidentate phosphine complexes. The effects of the arene, phosphine ligands and counter anions were investigated in regard to catalytic activity and selectivity. Selective dehydrogenation can occur via β-hydride elimination with the experimentally observed [(alkoxide)Ru] complex. [ABSTRACT FROM AUTHOR]

Hydroxynitrile lyases (HNLs) are increasingly finding application in the synthesis of enantiomerically pure cyanohydrins which are important intermediates in the production of pharmaceuticals and agrochemicals. Synthesis of enantiopure mandelonitrile was carried out using HNL of wild apricot ( Prunus armeniaca L.) [ ParsHNL] in aqueous/organic biphasic system. The optimum pH and temperature of the reaction were 4.0 and 15 °C respectively, which are important parameters to suppress the non-enzymatic catalysis. ParsHNL catalyses synthesis of ( R)-mandelonitrile in methyl- tbutyl ether (MTBE)/citrate buffer biphasic system with >99% ee. Synthesis of mandelonitrile was carried out in batch reaction at 40 ml scale and finally 2.7 mmoles of ( R)-mandelonitrile was recovered which corresponded to 90% molar conversion in 46 h reaction. In fed batch reaction 6.37 mmoles of ( R)-mandelonitrile could be produced which corresponds to 91% molar conversion in 46 h. In both reactions, enzyme produces ( R)-mandelonitrile with > 99% ee which showed enhanced selectivity as compared to aqueous reaction (96% ee) by ParsHNL. The results showed potential of ParsHNL to synthesize ( R)-mandelonitrile in both, batch reaction and fed-batch reaction and can be effectively used in the synthesis of ( R)-mandelonitrile. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The absolute stereochemistry of cyanohydrins, derived from ketones and aldehydes, is obtained routinely, in a microscale and derivatization-free manner, upon their complexation with Zn-MAPOL, a zincated porphyrin host with a binding pocket comprised of a biphenol core. The host-guest complex leads to observable exciton-coupled circular dichroism (ECCD), the sign of which is easily correlated to the absolute stereochemistry of the bound cyanohydrin. A working model, based on the ECCD signal of cyanohydrins with known configuration, is proposed. [ABSTRACT FROM AUTHOR]

Hydroxynitrile lyases (HNLs) are increasingly finding application in synthesis of enantiomerically pure cyanohydrins. Cyanohydrins are important intermediates in the production of pharmaceuticals and agrochemicals. In the present studies seeds of wild apricot ( Prunus armeniaca L.) have emerged as potential source of hydroxynitrile lyase. The HNL of wild apricot (ParsHNL) was purified 8.1 fold and 18.2 % yield with a specific activity of 141 units mg protein. The SDS-PAGE of the enzyme revealed that it consists of subunits of 40 and 37 kDa. However, the molecular weight of holoenzyme was assessed to be 360 kDa. The enzyme showed maximum activity in 0.1 M sodium-citrate buffer having pH 4.75 at 25 °C. Thermostability studies revealed that this HNL showed activity up to 70 °C temperature and quite stable up to 50 °C. Activation energy of ParsHNL was calculated to be 37.83 kJ mol. This enzyme has K of 3.76 mM, V of 188.4 µmol mg min and k of 1130.4 s using mandelonitrile as substrate while for reverse reaction using benzaldehyde as substrate it showed K of 16.1 mM, V of 7.21 µmol mg min and k of 43.3 s. Synthesis of mandelonitrile was carried out using ParsHNL and finally 8.88 mmole (1.184 g) of mandelonitrile was recovered which corresponded to 89 % molar conversion with 96 % ee for R-mandelonitrile. The yield of mandelonitrile was 411 µmol mgh. These results indicated that ParsHNL has very high potential for synthesis of cyanohydrins and can be used for the production of enantiopure cyanohydrins. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Background and Aims A major germination-promoting chemical in smoke-water is 3-methyl-2H-furo[2,3-c]pyran-2-one (karrikinolide, KAR1). However, not all species that germinate in response to smoke-water are responsive to KAR1, such as Tersonia cyathiflora (Gyrostemonaceae). In this study, a test was made of whether two Gyrostemon species (Gyrostemonaceae) that have previously been shown to respond to smoke-water, respond to KAR1. If not, then the smoke-derived chemical that stimulates germination of these species is currently unknown. Recently, glyceronitrile was isolated from smoke-water and promoted the germination of certain Anigozanthos species (Haemodoraceae). Whether this chemical promotes Gyrostemon racemiger germination is also examined. Furthermore, an investigation was carried out into whether these species germinate in response to smoke-water derived from burning cellulose alone. Methods Gyrostemon racemiger and G. ramulosus seeds were buried after collection and retrieved in autumn the following year when dormancy was alleviated and seeds had become responsive to smoke-water. Anigozanthos flavidus seeds were after-ripened at 35 °C to alleviate dormancy. Gyrostemon and Anigozanthos seeds were then tested with ‘Seed Starter’ smoke-water, KAR1, glyceronitrile and cellulose-derived smoke-water. Key Results Although Gyrostemon racemiger, G. ramulosus and A. flavidus were all stimulated to germinate by ‘Seed Starter’ smoke-water, none of these species responded to KAR1. Gyrostemon racemiger germination was not promoted by glyceronitrile. This is in contrast to A. flavidus, where glyceronitrile, at concentrations of 1–500 µm, promoted germination, although seedling growth was inhibited at ≥400 µm. Maximum A. flavidus germination occurred at glyceronitrile concentrations of 25–300 µm. Some Gyrostemon germination was promoted by cellulose-derived smoke-water. Conclusions KAR1 and glyceronitrile, chemicals in smoke-water that are known to stimulate germination in other species, did not promote the germination of G. racemiger. This suggests that other chemical(s) which promote germination are present in smoke, and may be derived from burning cellulose alone. [ABSTRACT FROM AUTHOR]

O-Protected cyanohydrins were found to serve as a source of the nitrile within the intramolecular cobalt-mediated [2+2+2] cycloaddition to pyridines. Several 6-substituted 1,2,3,4,7,8,9,10-octahydrophenanthridines were synthesized using this cycloaddition of diyne-cyanohydrins. By introduction a TMS group a divergent way to such phenanthridine derivatives was elaborated. [ABSTRACT FROM AUTHOR]

The alkali salt of L-proline was demonstrated to be an efficient and practical catalyst for the cyanosilylation of a wide variety of simple and functionalized carbonyl compounds under solvent-free conditions. The reactions proceeded smoothly at room temperature to afford the corresponding cyanohydrins in good to excellent yields. [ABSTRACT FROM AUTHOR]

Overexpression and production of the high concentration of hydroxynitrile lyase from cassava ( Manihot esculenta (MeHNL, EC 4.1.2.39)) were investigated. Hydroxynitrile lyase is a useful enzyme for the production of optically active cyanohydrin compounds. The production of MeHNL was increased by changing the rare codons of the original sequence of cassava MeHNL. However, most of the produced MeHNL was in the insoluble form. In order to increase the solubility of MeHNL, the effects of the cultivation temperature were investigated. When the cultivation temperature was reduced, the cell yield and the ratio of soluble MeHNL increased significantly. The enzyme activity and yield at low-temperature cultures (17 °C) were 850 times higher than those obtained at the optimum growth temperature of 37 °C. The rate of MeHNL production in the present study was calculated as 3,000 unit/h. Low-temperature cultivation was very effective in improving the productivity of the active form of MeHNL. Unlike the temperature-shift method, low-temperature cultivation has more potential for the large-scale production of MeHNL for the optically active cyanohydrin production. [ABSTRACT FROM AUTHOR]

The article reports on the expression of hydroxynitrile lyase from Manihot esculenta (MeHNL) in yeast and its application in (S)-Mandelonitrile production using an immobilized enzyme reactor. It states that MeHNL was cloned from a cDNA library prepared from a leaf of MeHNL which is then expressed in a multi-auxotrophic mutant of Saccaromyces cerevisiae cells. The author adds that Silica gel was the most appropriate support for immobilization of the prepared enzyme from the recombinant yeast.

The defatted seed meal of common vetch ( Vicia sativa L.) served as a source of ( R)-oxynitrilase which catalyzed the enantioselective addition of HCN to aromatic, heteroaromatic, fluoro-substituted aromatic aldehydes to produce the corresponding enantiomeric pure cyanohydrins in yields of 52–100% and 88–99% ee at 12°C under micro-aqueous medium (diisopropyl ether) without addition of buffer solution. [ABSTRACT FROM AUTHOR]

Benzil (1,2-diphenylethane-1,2-dione) undergoes cyanide catalyzed condensation with benzaldehyde to yield O-benzoylated benzoin (2-benzoyl-1,2-diphenylethanone). In this study, the experimentally suggested mechanism has been modeled with PM3 and verified with B3LYP. The effect of the substituent on the reaction yield has been rationalized by considering two benzil derivatives; 1,2-bis(2-chlorophenyl)ethane-1,2-dione and 1,2-bis(2-fluorophenyl)ethane-1,2-dione and three benzaldehyde derivatives; o-fluorobenzaldehyde, o-methylbenzaldehyde and 2-pyridinecarboxaldehyde. The effect of the solvent has been modeled by using the isodensity-surface polarizable continuum (IPCM) model. Reactivity descriptors have been used to justify the reactivity differences of the various substituents. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [ABSTRACT FROM AUTHOR]

The synthesis of optically active (R)-2-trimethylsilyl-2-hydroxyl-ethylcyanide by asymmetric trans-cyanation of acetyltrimethylsilane with acetone cyanohydrin in a biphasic system was achieved using (R)-oxynitrilase from loquat seed meal. Diisopropyl ether was the most suitable organic phase among the organic solvents examined. The optimal concentration of acetyltrimethylsilane, concentration of crude enzyme, volume ratio of the aqueous to the organic phase, temperature and the buffer pH value were 14 mM, 61.4 U ml-1, 13% (v/v), 30 °C and 4, respectively. The substrate conversion and the product enantiomeric excess were 95% and 98% under the optimized conditions. Acetyltrimethylsilane was a better substrate of the enzyme than its carbon counterpart. [ABSTRACT FROM AUTHOR]

Insecticidal fumigation toxicity of natural and synthetic cyanohydrins was evaluated with four stored-product pests: the lesser grain borer, Rhyzopertha dominica (F), the red flour beetle, Tribolium castaneum Herbst, the saw-toothed grain beetle Oryzaephilus surinamensis L, the maize weevil, Sitophilus zeamais (Motsch) and the house fly, Musca domestica L. The fumigation LC50 values were calculated by probit analysis. For house flies, all but one of the cyanohydrins tested were more potent than 1,3-dichloropropene (Telone®). Three were as efficacious as chloropicrin. For the lesser grain borer, all cyanohydrins tested were more insecticidal than dichloropropene, and all but one were more potent than chloropicrin. Four were as insecticidal as dichlorvos. The acetate of 1-cyano-1-hydroxy-2-propene (CHP-ace) was also tested in soil for antifungal and antibacterial activity, and inhibition of weed seed germination. CHP-ace reduced the total soil bacterial and fungal counts significantly, and was effective in inhibiting the germination of weed seeds in soil, indicating a broad spectrum of activity as a soil fumigant. [ABSTRACT FROM AUTHOR]

Optically active 2-trimethylsilyl-2-hydroxyl-ethylcyanide was prepared by enzymatic enantioselective transcyanation of acetyltrimethylsilane with acetone cyanohydrin in a biphasic system at 35 °C and pH 5. (R)-Oxynitrilase from apple seed meal was the best among all the enzymes explored and diisopropyl ether was the most suitable organic phase. Acetyltrimethylsilane was a better substrate of the enzyme than its carbon analogue. The substrate conversion and product enantiomeric excess of 2-trimethylsilyl-2-hydroxyl-ethylcyanide were >99% and >99%, respectively. [ABSTRACT FROM AUTHOR]

Enantiotopic group selectivity can result from the competition between substrate and reagent double stereodifferentiation. We have examined this approach for enantioselective hydrocyanation of racemic α-alkoxy aldehydes (e.g., 2-(phenylmethoxy)heptanal (1)). Reaction of 1 with TMSCN mediated by chiral nonracemic alkoxy Ti(IV) reagents under conditions known to be reasonably enantioface selective in reactions with achiral aldehydes, proceeded with very low enantiotopic group selectivity (<2:1). It was established that TMSCN can react with Ti(IV) reagents to produce "TiCN" adducts that are capable of hydrocyanation but with low substrate-controlled diastereoselectivity in reactions with 1. The poor enantiotopic group selectivity observed can be rationalized to result from this low diastereoselectivity despite the respectable levels of enantioface selectivity associated with these reagents in hydrocyanation of achiral aldehydes. Highly diastereoselective hydrocyanation of α-alkoxy aldehydes can be achieved with TMSCN in the presence of excess MgBr[sub 2] ·OEt[sub 2] . High diastereoselectivity was also observed using achiral and chiral TiCN adducts in place of TMSCN. Although the putative TiCN adducts obtained from nonracemic alkoxy Ti(IV) reagents are implicated in enantioface selective hydrocyanation, these reagents were not enantiotopic group selective under these conditions and showed no evidence of double stereodifferentiation. The use of nonracemic bisoxazoline ligands for Mg(II) was also ineffective.Key words: cyanohydrin, 2-alkoxyalkanal, double stereodifferentiation, enantiotopic group selective reaction, kinetic resolution.La sélectivité énantiotopique de groupe peut découler d'une compétition entre la stéréodifférenciation double entre le substrat et le réactif. On a examiné cette approche pour l'hydrocyanuration énantiosélective d'α-alkoxy aldéhydes racémiques (par exemple, le 2-(phénylméthoxy) heptanal (1)). Lors de la réaction avec le TMSCN, sous l'influence de réactifs chiraux non racémiques de type alkoxy Ti(IV), dans des conditions reconnues pour être énantiosélectives au cours de réactions avec les faces d'aldéhydes achiraux, la sélectivité énantiotopique de groupe était très faible (< 2:1). Il a été établi que le TMSCN peut réagit avec les réactifs du Ti(IV) pour conduire à la production d'adduits "TiCN" qui, lors de réactions avec le composé 1, peuvent donner lieu à une hydrocyanuration pour laquelle la diastéréosélectivité contrôlée par le substrat est faible. On peut imaginer que la faible sélectivité énantiotopique de groupe observée résulte de cette faible diastéréosélectivité malgré les niveaux respectables de énantiosélectivité par rapport aux faces qui sont associées à ces réactifs dans l'hydrocyanuration d'aldéhydes achiraux. On peut réaliser des hydrocyanurations hautement diastéréosélectives d'α-alkoxyaldéhydes à l'aide de TMSCN, en présence d'un excès de MgBr[sub 2] ·OEt[sub 2] . On a aussi observé une diastéréosélectivité lorsqu'on a utilisé des adduits TiCN achiraux et chiraux à la place du TMSCN. Les adduits TiCN présumés, obtenus à partir de réactifs non racémiques de type alkoxy Ti(IV), sont impliqués dans des hydrocyanurations énantiosélectives par rapport aux faces; toutefois, dans ces conditions, ces réactifs ne donnent pas lieu à de la sélectivité énantiotopique de groupe et ne présentent pas de signe de double stéréodifférenciation. L'utilisation de ligands bisaxozolines non racémiques pour des composés de type Mg(II) est aussi inefficace.Mots clés : cyanohydrine, 2-alkoxyalcanal, double stéréodifférenciation, réaction avec sélectivité énantiotopique de groupe, dédoublement cinétique.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A novel organocatalytic multicomponent cyanovinylation of aldehydes was designed for the synthesis of conjugated cyanomethyl vinyl ethers. The reaction was implemented for the synthesis of a 3-substituted 3-(cyanomethoxy)acrylates, using aldehydes as substrates, acetone cyanohydrin as the cyanide anion source, and methyl propiolate as the source of the vinyl component. The multicomponent reaction is catalyzed by N-methyl morpholine (2.5 mol%) to deliver the 3-(cyanomethoxy)acrylates in excellent yields and with preponderance of the E-isomer. The multicomponent reaction manifold is highly tolerant to the structure and composition of the aldehyde (aliphatic, aromatic, heteroaromatics), and it is instrumentally simple (one batch, open atmospheres), economic (2.5 mol% catalyst, stoichiometric reagents), environmentally friendly (no toxic waste), and sustainable (easy scalability). [ABSTRACT FROM AUTHOR]

The hydroxynitrile lyase (HNL, EC 4.2.1.-) of Hevea brasiliensis (Muell.-Arg.) catalyzes the dissociation of acetone cyanohydrin and mandelonitrile, but shows higher activity towards the natural substrate acetone cyanohydrin. The ratio between the activities of linamarase (β-gIycosidase, EC 3.2.1.21) to HNL was screened for more than 30 Hevea plants. In mixed-enzyme incubations various ratios of HNL to β-glucosidase were analyzed for the rapidity of HCN liberation. Addition of HNL increased the rate of HCN liberation up to 20-fold, thus demonstrating the significance of the HNL for rapid cyanogenesis. Its physiological importance is shown by the fact that only plants possessing high HNL activity are able to liberate HCN efficiently. Cyanogenic plants have been described as being weakly or strongly cyanogenic depending on the total amount of HCN which is potentially liberated. The data presented in this paper suggest that cyanogenic plants should also be differentiated as fast or slow cyanogenic according to the observed velocity of HCN liberation. Thus, for evaluating the rapellent action of cyanogenic plants not only the final level of the HCN liberated is important but rather the rate with which this level is reached. [ABSTRACT FROM AUTHOR]

The hydroxynitrile lyase from Prunus amygdalus was immobilized on Celite R-633. The immobilized enzyme could successfully be utilized in buffer saturated MTBE and excellent conversions of benzaldehyde to R-mandelonitrile were observed. No leaching occurred. To achieve high enantioselectivities, the suppression of the undesired background reaction was essential. This could be achieved by high enzyme loadings and the tight packing of the immobilized enzymes. When the immobilized enzyme is loosely packed, both the enzyme catalysis and the background reaction accelerates and only a modest enantioselectivity is observed. The enzyme was recycled for up to ten times, with some loss of activity and also enantioselectivity after 5 cycles, independent of packing. [ABSTRACT FROM AUTHOR]

The front cover picture, provided by Kicheol Kim, illustrates the development of a ruthenium catalytic system for acyl cyanide synthesis via acceptorless dehydrogenation of cyanohydrins. As opposed to the thermodynamically preferred elimination of hydrogen cyanide, the dehydrogenation of cyanohydrins could be kinetically controlled with ruthenium(II) bidentate phosphine complexes. Effects of ligands and counter anions in the ruthenium catalyst were investigated to modulate catalytic activity and selectivity. Details can be found in the communication on pages 3292 – 3298 (K. Kim, A. M. P. Moeljadi, H. Hirao, S. H. Hong, Adv. Synth. Catal. 2017, 359, 3292 – 3298; DOI: 10.1002/adsc.201700786). [ABSTRACT FROM AUTHOR]

The article presents a study which examines the hydroxynitrile lyase (HNL) activity of defatted Prunus seeds in producing optically active cyanohydrins. It explores enzymatic activity of the HNL source of defatted seed catalyzing the formation of mandelonitrile from benzaldehyde. It also looks into the effects of the defatted capulin seeds and other substituents on the extent of the biocatalyzed selective addition of cyanide to aldehydes and aromatic compounds.