Acetone Cyanohydrin Research Articles

Effects of fermentation and storage upon levels of intermediate cyanide (cyanohydrins) in cassava flour

The effects of fermentation of cassava on cyanide content were evaluated. Total cyanide decreased from 89ppmHCN to 18.1ppmHCN (80% reduction). Free cyanide decreased from 8.71ppmHCN to 6.22ppmHCN (29% reduction). The intermediate cyanide increased from 10.2ppmHCN to 12.31 ppm HCN (21% increase). The effects of storage of cassava augmented with exogenous acetone cyanohydrin and stored at 30°C was also investigated. Acetone cyanohydrin (intermediate cyanide) decreased on storage from 302.9 ppm HCN to 168.9 ppm HCN (44% reduction) within 16 days. Very little change in acetone cyanohydrin was observed in flour kept at 18°C (control). This investigation indicates that storage reduces the intermediate cyanide content of cassava flour which remains after fermentation.

Studies on the quantification of specific cyanogens in cassava products and introduction of a new chromogen

AbstractThe enzymic assay for cyanogens in cassava as developed by Cooke (1978) and improved by O'Brien et al (1991), was compared with a standard method, involving autolysis/steam distillation/titration, and further improved with a more acceptable coloration and other minor changes. Cooke's assay, using a linamarin calibration curve, gave similar values for cyanogenic potential in fresh cassava as the standard method. For cassava samples with high non‐glycosidic cyanogen levels, Cooke's assay yielded slightly lower values. Isonicotinate/1,3‐dimethyl barbiturate as reagent in the König reaction had the following advantages compared with the so far applied pyridine/pyrazolone color reagent. It is less toxic and does not release repulsive vapours. It is faster, cheaper and easier to handle, and has increased sensitivity and longer storability. Direct measurement of cyanogenic potential was accurate in extracts containing 35–700 μM. Recovery of linamarin supplements was 102±4%. Separate calibration curves of linamarin, acetone cyanohydrin and KCN were necessary for accurate calculation of cyanogenic glycosides and cyanohydrin levels. Extract storability depended slightly on storage temperature, but was not changed by inclusion of ethanol in the extract medium.

Degradation of cassava linamarin by lactic acid bacteria

Summary Six out of ten lactic acid bacteria strains tested displayed linamarase activity. Lactobacillusplantarum strain A6 displayed the greatest activity affecting 36 U/g cells on MRS cellobiose. The strain also broke down in less than 2 hours the linamarin ex- tracted from cassava juice. HPLC analysis ofthe products of the reaction showed that the bacteria converted the linamarin into lactic acid and acetone cyanohydrin.

Regiospecific opening of 1,2-expoxides with acetone cyanohydrin under mildly basic conditions

Acetone cyanohydrin with stoichiometic triethylamine opens epoxides regiospecifically to give β-hydroxy nitriles. As expected, addition of cyanide occurs at the least substituted carbon.

One-Pot Synthesis of Optically Active Cyanohydrin Acetates from Aldehydes via Quinidine-Catalyzed Transhydrocyanation Coupled with Lipase-Catalyzed Kinetic Resolution in Organic Solvent

Abstract A novel one-pot synthetic method was developed for the preparation of optically active cyanohydrin acetates. Racemic cyanohydrins were generated from aldehydes and acetone cyanohydrin by quinidine-catalyzed transhydrocyanation, and the resulting cyanohydrins 2a–j were then acetylated by lipase in a stereoselective manner using isopropenyl acetate as an acylating regent. A variety of aldehydes 1a–j were successfully transformed into the corresponding cyanohydrin acetates 3a–j having 47–95% e.e. without isolating the unstable cyanohydrins 2. Moreover, the reversible nature of base-catalyzed transhydrocyanation allows for in situ racemization of the unreacted cyanohydrins and concurrent kinetic resolution by lipase enabled the preparation of (S)-3b–d with 40–82% e.e. in more than 50% yield. Polymer-supported cinchona alkaloid was also used as a catalyst for this one-pot reaction and showed the comparable chemical and optical yield to that for the soluble monomeric alkaloid. The insoluble polymer and lipase were recovered by filtration and found to have almost the same catalytic activity even after four times of reuse.

ChemInform Abstract: Cyano Group Transfer of Acetone Cyanohydrin (II) to Aldehyde (I) Mediated by Titanium Alkoxide.

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Synthesis of 1-amino-2,2-dialkylcyclopropanecarboxylic acids from β-chloroaldimines

A variety of hydrogen cyanide adducts of β-chloroaldimines using acetone cyanohydrin were prepared. The reactive behaviour of these α-amino-γ-chloronitriles towards bases was investigated with the aim to generate 1-aminocyclopropanecarbonitriles, which are precursors for the potentially plant growth regulating 1-aminocyclopropanecarboxylic acids. The synthesis of 1-amino-2,2-dimethylcyclopropanecarboxylic acid (= 2,3-methanovaline) by a reaction sequence involving addition of hydrogen cyanide across β-chloroaldimines, ring closure to functionalized cyclopropanes and acidic hydrolysis was accomplished. Alternatively the hydrogen cyanide adducts of β-chloroaldimines were converted into α-(N-benzylidene)amino-γ-chloronitriles, which were ring closed with base and hydrolyzed to afford 1-amino-2,2-dialkylcyclopropanecarbonitriles, the latter serving again as substrates for the hydrolytic conversion into the corresponding 1-amino-2,2-dialkylcyclopropanecarboxylic acids (exemplified for 1-amino-2,2-dimethylcyclopropanecarboxylic acid).

A Novel Rate Enhancement in Titanium and Zirconium Alkoxide Mediated Cyano Group Transfers by the Addition of a Salycylal Type Schiff Base, dl-3-(2-Hydroxy-1-naphthylidene)-imino-ε-caprolactam. A Neighboring Amide Effect

Abstract The addition of a salycylal type Schiff base containing amide, dl-3-(2-hydroxy-1-naphthylidene)-imino-ε-caprolactam (Nap-ACL) to titanium (IV) 2-propoxide or zirconium (IV) 1-propoxide accelerates cyano group transfers of acetone cyanohydrin with various carbonyl and imino compounds to give the corresponding cyanated products.

Stereospecificity of the addition of hydrogen cyanide to the carbonyl group of substituted 4-piperidones. Synthesis and three-dimensional structures of substituted 4-hydroxy-4-cyanopiperidines

Mixtures of stereoisomers of the corresponding 4-hydroxy-4-cyanopiperidines were synthesized by the reaction of substituted 4-piperidones with hydrogen cyanide by an exchange reaction with acetone cyanohydrin. The ratios of the stereoisomers in the resulting mixtures of stereoisomeric 4-piperidone cyanohydrins were determined by means of the 13C NMR spectra, and the three-dimensional structures were established by direct determination of the orientation of the cyano group in their molecules. A dependence of the quantitative ratios of the stereoisomeric cyanohydrins of the substituted 4-piperidones on the reaction temperature was demonstrated.

Cyano Group Transfer of Acetone Cyanohydrin to Aldehyde Mediated by Titanium Alkoxide and Aluminum Alkyls

Abstract Cyano group transfer reaction of acetone cyanohydrin to various aldehydes in the presence of titanium alkoxide and aluminum alkyls to give the corresponding aldehyde cyanohydrins in high yield is described.

ChemInform Abstract: Reaction of Citral with Acetone Cyanohydrin and Diethylamine and Thermolysis of the Amino Nitrile Formed.

AbstractThe aldehyde (I) reacts with acetone cyanohydrin (II) under exchange of the cyano group, yielding acetone and the cyanohydrin of (I) which is directly aminated to give the amino nitriles (IV).

The chemistry of 9α-hydroxysteroids. 3. Methods for selective formation and dehydrations of 17β-cyano-9α,17α-dihydroxyandrost-4-en-3-one

Two methods to produce the 17-cyanohydrin, using potassium cyanide in acetic acid/methanol or acetone cyanohydrin with aqueous sodium hydroxide, were followed with 9α-hydroxyandrost-4-ene-3,17-dione, both providing 17β-cyano-9α,17α-dihydroxyandrost-4-en-3-one. The selectivity of one of these methods, that which uses acetone cyanohydrin, is not in agreement with a comparable reaction with the 9α-unsubstituted androst-4-ene-13,17-dione to give the 17α-cyano-17β-hydroxy product, as reported in the literature and confirmed by us. The 9α-hydroxy and 17α-hydroxy groups were used for the regioselective introduction of 9(11)- and 16(17)-double bonds by dehydrating 17β-cyano-9α,17α-dihydroxyandrost-4-en-3-one under different conditions.

Factors that determine rates of cyanogenesis in bovine ruminal fluid in vitro.

Strained ruminal fluid was collected from cattle fed five diets at two locations to determine in vitro rates of cyanogenesis from the glycosides amygdalin, prunasin and linamarin. Rates of dissociation for the corresponding aglycones, benzaldehyde cyanohydrin and acetone cyanohydrin, also were determined. Hydrogen cyanide (HCN) in ruminal fluid was determined with a modified method of HCN analysis that independently measured the overall rate of cyanogenesis and the nonenzymatic dissociation of cyanohydrins, the intermediate products in the degradation of cyanogenic glycosides to HCN. Rate of dissociation of cyanohydrins in ruminal fluid was pH-dependent, with high rates of dissociation (as expressed by the rate constant or half-life of the reaction) occurring at pH greater than 6 and slower rates at pH 5 to 6. Cyanohydrin dissociation was most rapid when cattle were fasted for 24 to 48 h and ruminal pH was high; rate of dissociation was much slower during feeding and digestion. When the glycosides were examined, highest rates of cyanogenesis (mg HCN.liter-1.s-1) were observed after a 24-h postprandial period. Hence, cattle are most susceptible to poisoning by cyanogenic plants when the pH of ruminal fluid is elevated (for rapid dissociation) and also when the activity of microbial beta-glucosidase is adequate for rapid hydrolysis of glycosidic bonds. Rates of cyanogenesis were higher when ruminal inocula were from cattle fed fresh alfalfa or cubed alfalfa hay rather than grain or long hay. Rates of HCN production were slowest using inocula from cattle fed grain; rates for the three glycosides were negligible at the 3 and 6 h postprandial sampling times.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyanation of halo derivatives by acetone cyanohydrin

A preparative method is proposed for the synthesis of substituted acetonitriles by the cyanation of halo derivatives by acetone cyanohydrin in the presence of base and phase transfer catalysts.

Reaction of citral with acetone cyanohydrin and diethylamine, and thermolysis of the resulting aminonitrile

The reactions of citral with acetone cyanohydrin and secondary amines (diethylamine, piperidine, morpholine, and N-methylaniline) to give 2-substituted amino-4, 8-dimethyl-3,7-nonadienoic acid nitriles have been examined. Possible path-ways for these reactions are discussed. The thermolysis of 2-diethylamino-4,8-dimethyl-3, 7-nonadienoic acid nitrile has been examined in solution, to give irreversibly 3-cyano-1-diethylamino-3,7-dimethyl-1,6-octadiene, this reaction proceeding faster in polar than in nonpolar solvents.

Mandelonitrile lyase from Ximenia americana L.: stereospecificity and lack of flavin prosthetic group.

A mandelonitrile lyase (EC 4.1.2.10) that catalyzes the dissociation of (S)-(-)-mandelonitrile to benzaldehyde and hydrogen cyanide has been purified to apparent homogeneity from leaves of Ximenia americana L. (Olacaceae). The lyase was purified 122-fold with 38% yield by chromatography on carboxymethyl-cellulose and chromatofocusing. The enzyme had a pH optimum of 5.5, with a Km value of 280 microM. Activity toward 4-hydroxy-(R,S)-mandelonitrile was 77% of that observed with the endogenous substrate; no activity was observed toward the aliphatic substrate acetone cyanohydrin. The enzyme was stable at 4 degrees C and at room temperature for at least 1 month. Native and subunit molecular weights of 38,000 and 36,500, respectively, suggest the enzyme is a monomer. The isoelectric point was pH 3.9 as determined by isoelectric focusing. Staining with periodic acid-Schiff and fluorescein-labeled concanavalin A reagents indicate this enzyme is a glycoprotein. In contrast to (R)-mandelonitrile lyases isolated from Prunus species, the Ximenia lyase does not appear to be a flavoprotein. A second enzyme that eluted from the chromatofocusing column at pH 4.0 was also active toward mandelonitrile. However, this form accounted for less than 10% of the total activity, and its specific activity was only 6% of that of the major component. Additional physical and kinetic studies suggested this activity may be due to a nonspecific enzyme that is active toward mandelonitrile.

ChemInform Abstract: Stereoselective Syntheses of 2‐Deoxy‐β‐C‐arabino‐ and ribopyranosides: 2‐Deoxy‐β‐arabino‐ and ‐ribopyranosyl Cyanides

2-Deoxy-β-arabino- and ribopyranosyl cyanides, which should be suitable for the syntheses of biologically active products, were stereoselectively prepared from the reaction of the enones, 1,5-anhydro-2-deoxy-erythro-hex-1-en-3-ulose derivatives, with acetone cyanohydrin, followed by the stereoselective reduction of the producing ketones with NaBH4–CeCl3·7H2O and L-Selectride, respectively.

ChemInform Abstract: A New Synthetic Route to 4,6‐Diarylpyridazinones and Some of Their Derivatives.

AbstractThe chalcones (I) react with acetone cyanohydrin (II) to give the addition products (III) which are hydrolyzed to form the carboxylic acids (IV).

Stereoselective Syntheses of 2-Deoxy-β-C-arabino- and ribopyranosides: 2-Deoxy-β-arabino- and ribopyranosyl Cyanides

Abstract 2-Deoxy-β-arabino- and ribopyranosyl cyanides, which should be suitable for the syntheses of biologically active products, were stereoselectively prepared from the reaction of the enones, 1,5-anhydro-2-deoxy-erythro-hex-1-en-3-ulose derivatives, with acetone cyanohydrin, followed by the stereoselective reduction of the producing ketones with NaBH4–CeCl3·7H2O and l-Selectride, respectively.

α‐Hydroxynitrile lyase in Hevea brasiliensis and its significance for rapid cyanogenesis

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‐glycosidase, 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 repellent 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.