Absence Of Aldehyde Research Articles

Hydrogen‐Bond‐Driven Controlled Molecular Marriage in Covalent Cages

A supramolecular approach that uses hydrogen-bonding interaction as a driving force to accomplish exceptional self-sorting in the formation of imine-based covalent organic cages is discussed. Utilizing the dynamic covalent chemistry approach from three geometrically similar dialdehydes (A, B, and D) and the flexible triamine tris(2-aminoethyl)amine (X), three new [3+2] self-assembled nanoscopic organic cages have been synthesized and fully characterized by various techniques. When a complex mixture of the dialdehydes and triamine X was subjected to reaction, it was found that only dialdehyde B (which has OH groups for H-bonding) reacted to form the corresponding cage B3X2 selectively. Surprisingly, the same reaction in the absence of aldehyde B yielded a mixture of products. Theoretical and experimental investigations are in complete agreement that the presence of the hydroxyl moiety adjacent to the aldehyde functionality in B is responsible for the selective formation of cage B3X2 from a complex reaction mixture. This spectacular selection was further analyzed by transforming a nonpreferred (non-hydroxy) cage into a preferred (hydroxy) cage B3X2 by treating the former with aldehyde B. The role of the H-bond in partner selection in a mixture of two dialdehydes and two amines has also been established. Moreover, an example of unconventional imine bond metathesis in organic cage-to-cage transformation is reported.

ChemInform Abstract: Direct Formation of Cycloadducts Between Fullerenes and Amino Acids Through Electron‐Transfer Processes.

Abstract The reactions of [60]fullerene and amino acids in the absence of aldehyde in o-dichlorobenzene (ODCB) at 150 °C have been investigated. Fulleropyrrolidines 1 [C60(CH2N(CH3)CHC6H2(NO2)3)], 2 [C60(CH2N(CH3)CH2)], 3 [C60(CH2NHCH2)], and 5a–b [C60(RCHNHCHR), R˭CH3 (5a), R˭CH2Ph (5b)] were obtained in moderate yields from the reactions of C60 and corresponding amino acids. The reaction of C70 and N-methylglycine in the absence of aldehyde was also studied and was found to give the positional isomers of N-methyl[70]fulleropyrrolidines 6 (1,9-isomer) and 7(7,8-isomer). All products were fully characterized by ultraviolet–visible, Fourier transform–infrared (FT-IR), NMR, and mass spectrometry. The reactions were also carried out in the dark to exclude the possible interference of the photoinduced reactions, and almost the same yields of products were obtained.

Direct Formation of Cycloadducts Between Fullerenes and Amino Acids Through Electron-Transfer Processes

The reactions of [60]fullerene and amino acids in the absence of aldehyde in o-dichlorobenzene (ODCB) at 150 °C have been investigated. Fulleropyrrolidines 1 [C60(CH2N(CH3)CHC6H2(NO2)3)], 2 [C60(CH2N(CH3)CH2)], 3 [C60(CH2NHCH2)], and 5a–b [C60(RCHNHCHR), R˭CH3 (5a), R˭CH2Ph (5b)] were obtained in moderate yields from the reactions of C60 and corresponding amino acids. The reaction of C70 and N-methylglycine in the absence of aldehyde was also studied and was found to give the positional isomers of N-methyl[70]fulleropyrrolidines 6 (1,9-isomer) and 7(7,8-isomer). All products were fully characterized by ultraviolet–visible, Fourier transform–infrared (FT-IR), NMR, and mass spectrometry. The reactions were also carried out in the dark to exclude the possible interference of the photoinduced reactions, and almost the same yields of products were obtained.

Study of a specific lignin model: γ-Oxidation and how it influences the hydrolysis efficiency of alcohol–aldehyde dehydrogenation copolymers

Six coniferyl alcohol–coniferaldehyde dehydrogenation copolymers (DHcoPs) were synthesized in order to determine the influence of an increased number of aldehyde functions on hydrolysis. After heterogeneous hydrolysis using acidic Montmorillonite K10 clay, the DHcoPs were thioacidolyzed and analyzed by gel permeation chromatography (GPC). Comparison of the thioacidolyzed products, with and without the hydrolysis step, showed that there was a greater proportion of condensation reaction in the absence of aldehyde. When the coniferaldehyde content in the initial synthetic mixture was more than 30% (w/w), only a low fraction of condensed products was generated during the K10 clay hydrolysis step. This suggests that condensation pathways are mainly due to the alcohol present in the γ-position in the DHcoPs. Investigation of the reactivity and the potential condensation of aldehyde and alcohol monomers under hydrolysis conditions showed the important conversion of coniferyl alcohol and conversely the stability of coniferaldehyde.

Synthesis of Trimetasphere Pyrrolidino Derivatives: Reaction of Lu3N@C80 with N-Ethylglycine in the Presence and Absence of Aldehyde

The [2+3] cycloaddition reaction was studied on Lu3N@C80 with N-ethylglycine in the presence and absence of aldehyde. Both reactions afforded the same symmetrical [5, 6] fulleropyrrolidine adduct. However, the reaction on C60 with N- ethylglycine in the absence of aldehyde formed a methanofullerene derivative and a fulleropyrrolidine derivative.

Lewis Acid–Lewis Base‐Catalysed Enantioselective Addition of α‐Ketonitriles to Aldehydes

AbstractAdditions of structurally diverse α‐ketonitriles to aromatic and aliphatic prochiral aldehydes yielding highly enantioenriched acylated cyanohydrins were achieved using a combination of a titanium salen dimer and an achiral or chiral Lewis base. In most cases high yields and high enantioselectivities were observed. The ee was moderate in the initial part of the reaction but increased over time. This could be avoided, and higher ees obtained, by keeping the titanium complex, in the presence or absence of aldehyde and ketonitrile, at −40 °C prior to the addition of the Lewis base. A mechanism initiated by nucleophilic attack of the tertiary amine at the carbonyl carbon atom of the ketonitile is supported by 13C labelling experiments.

Interaction of bacterial luciferase with aldehyde substrates and inhibitors.

Bacterial luciferase catalyzes the reaction of FMNH2, O2, and an aliphatic aldehyde to yield the carboxylic acid, FMN, water and blue-green light. The kinetics of the bacterial luciferase reaction were measured by stopped-flow spectrophotometry at pH 7 and 25 degrees C for the series of aldehydes from n-heptanal to n-undecanal. The rate of formation of the 4a-hydroperoxyflavin intermediate was dependent on the aldehyde concentration when mixtures of enzyme, FMNH2, and aldehyde were rapidly mixed with O2. At saturating aldehyde, the rate of formation of this intermediate was 100-fold slower than in the absence of aldehyde, demonstrating that an enzyme.FMNH2.aldehyde complex can be formed. Numerical simulation of the time courses for these experiments supported the formation of this intermediate and its direct reaction with O2. The kinetics of the light emitting reaction were dependent upon the chain length of the aldehyde substrate. Although the initial light intensity and the light emission decay rate were different for each aldehyde, the quantum yield for the reaction was independent of the aldehyde used. Luciferase was inhibited by high levels of the aldehyde substrate when the enzyme was assayed by mixing FMNH2 with an aerobic mixture of enzyme and aldehyde. The extent of inhibition was dependent on the particular aldehyde used, and the binding affinity of the aldehyde for the free enzyme increased in parallel with the aldehyde chain length. The kinetics of the formation and decay of the various intermediates were also studied in the presence of n-alkyladehyde analogs. These compounds decreased the rate of formation of the 4a-hydroperoxyflavin intermediate in much the same way as the aldehyde substrate, presumably by the formation of the enzyme.FMNH2.analog ternary complex.

Luminescence of a bacterial luciferase intermediate by reaction with H 2O 2: the evolutionary origin of luciferase and source of endogenous light emission

The bacterial luciferase reaction was shown to emit light in the presence of hydrogen peroxide (H 2O 2) instead of aldehyde. Although the light intensity was weaker than that with an aldehyde, the bioluminescence emission spectrum of the luciferase reaction ( λ max 495 nm) with H 2O 2 closely agreed with that using a long chain aliphatic aldehyde (decanal). It was also found that the chemiluminescence of reduced or unreduced FMN with H 2O 2 was enhanced by peroxidase. Light emission in the luciferase reaction with H 2O 2 is attributed to a catalase-like reaction, in which the abstraction of one atom of oxygen from intermediate II (luciferase-bound FMNH-OOH) by H 2O 2 leads to the formation of excited hydroxide (E-FMNH-OH∗), H 2O and O 2. Since H 2O 2 is formed in the spontaneous breakdown of intermediate II in the absence of aldehyde, the reaction of this H 2O 2 with intermediate II can explain the origin of endogenous (non aldehyde) light emission. In the presence of luciferase, intermediate II can be formed both from FMNH 2 and oxygen, and by the reaction of H 2O 2 with FMN. The functional origin of the bacterial luciferase is postulated to be a FMN-dependent non-heme catalase which scavenges H 2O 2, concomitant with weak light emission. Prior to the association of luciferase genes ( lux AB) with the aldehyde synthesis genes ( lux CDE), forming the lux operon in luminous bacteria, the genes may have been expressed independently such that the bacteria lacked a high level of light emission.

The reaction of trihalogenomethyl anions with carbonyl compounds: competitive reactivity comparisons and applications to the synthesis of α-trihalogenomethyl alcohols

Trihalogenomethyl anions, generated by decarboxylation of trichloro- and tribromo-acetic acid in dimethyl sulphoxide solution, react with added aldehydes. In the presence of 1,3,5-trinitrobenzene, the reaction with aldehydes competes with the formation of the coloured Meisenheimer adduct. The reduction in absorbance from the value in the absence of aldehyde has been used to measure the reactivity of trihalogenomethyl anions towards a series of aldehydes relative to their reactivity towards trinitrobenzene. For 4-substituted benzaldehydes, the reactivities obey a linear ρσ– relationship. The most reactive aldehyde used is only two times less reactive towards CCl3– or CBr3– than hydrogen ions, and it is concluded that, in dimethyl sulphoxide solutions, the reaction between trichloromethyl anions and hydrogen ions is not encounter-controlled. The reactions with aldehydes have been used to prepare several new compounds of the formula RCH(OY)CX3 where R = aryl or pyridyl, X = Br or Cl, and Y = H or COCH3.

Fluorescent compounds in the protein skeleton of a gorgonian coral and their possible role in cross-linking

1. 1. Fractionation of both acid and alkaline hydrolysates of a gorgonian skeleton yields three blue-fluorescent compounds. 2. 2. Absorption, fluorescence and mass spectra indicate that the fluors are substituted benzenoid compounds. 3. 3. Chemical tests indicate the absence of aldehyde, hydroxyl, amino and indole groups, and the presence of carboxyl groups. 4. 4. The possible role of such compounds in cross-linking of the skeleton are discussed and compared with other known or suspected protein tanning agents.

Studies on luciferase from Photobacterium phosphoreum. X. Heat of formation of the intermediate in the bioluminescent reaction studied by stopped-flow calorimetry.

The heat production in the reaction of luciferase-FMNH2 complex with O2 in the absence of aldehyde was measured by stopped-flow calorimetry. deltaH of the reaction, luciferase-FMNH2+ O2 leads to intermediate X1, is -1.3 X 10(2) kJ.mol-1 and the calculated deltaS for the reaction is -180 J.mol-1.K-1 at 20 degrees C. The heat production in the bioluminescent reaction was also measured in the presence of a saturating concentration of aldehyde, and it was estimated that 43 and 79% of the C10 and C13 aldehydes, respectively, bound with the intermediate X1 are converted to carboxylic acid yielding energy for photon emission.

Intermediates in the bacterial luciferase reaction

Rapid formation of an unstable, intermediary state of an enzyme complex, which is obligatory in the bacterial luciferase reaction, was observed on aerobic oxidation of the luciferase-FMNH 2 complex. The rate of decay of this intermediate in the absence of aldehyde was measured. The value obtained coincided with that estimated from the decay of the peak intensity of luminescence observed on addition of aldehyde at intervals after mixing the luciferase-FMNH 2 complex with O 2. A sequential mechanism of the reaction of bacterial luciferase is discussed.

Enzymatic properties of bacterial luciferase

1. 1. The present report is concerned with some of the enzymatic properties of highly purified bacterial luciferase, an enzyme which catalyzes a light-emitting reaction in the presence of reduced riboflavin phosphate (FMNH 2), a long-chain fatty aldehyde, and oxygen. Reduced diphosphopyridin nucleotide (DPNH) or triphosphopyridine nucleotide (TPNH) will support luminescence if FMN is added to the reaction mixture. 2. 2. Various reduced dyes such as safranine T, indigotrisulfonate, and rosindulin 2G, as well as reduced riboflavin, will also reduce FMN and support luminescence provided aldehyde is added. 3. 3. In the absence of aldehyde and FMN, the bacterial luciferase catalyzes the reduction of methylene blue, various quinones, and ferricyanide by DPNH. If ferricyanide is added to a normal reaction mixture, no light is emitted until the ferricyanide is reduced. Because of the autoxidation of FMNH 2 luciferase rapidly catalyzes the oxidation of DPNH in the presence of FMN. 4. 4. The kinetics of light emission starting with reduced FMN indicate that two FMNH 2 molecules combine with luciferase. Two different equations have been derived which describe the results, and the various dissociation constants have been calculated. 5. 5. The relationship between light intensity and enzyme concentration using both DPNH and FMNH 2 was determined. With FMNH 2 the light intensity is proportional to enzyme concentration, while with DPNH a nonlinear response is observed. This latter result is due presumably to the greater autoxidation of FMNH 2, which is formed from DPNH and FMN, at low enzyme concentration. 6. 6. With the purified enzyme, light emission is dependent upon a supply of aldehyde. Dodecyl aldehyde has been used in all of the present experiments. By using appropriate dilutions of the substrate, it is possible to show that the total light emitted depends upon the aldehyde concentration. The aldehyde is presumably oxidized to the acid; however, because of the small quantities used it is not possible to establish this point directly. 7. 7. Yeast alcohol dehydrogenase in the presence of DPNH catalyzes the reduction of the long-chain aldehydes to the corresponding alcohols. 8. 8. The possibility that the aldehyde combines with FMNH 2 to form an intermediate which is peroxidized by a flavin radical is discussed as a mechanism for light emission.