Catalyzed Condensation Reaction Research Articles

Identification of a disruptor of the MDM2-p53 protein–protein interaction facilitated by high-throughput in silico docking

NSC 333003 has been identified from the NCI Diversity Set as an inhibitor of the MDM2-p53 protein–protein interaction by in silico docking (virtual screening). Its potency and chemical characteristics render it well suited for lead optimization studies that can result in more potent analogs with improved drug-like properties. Its synthesis was achieved using an acid catalyzed condensation reaction from commercially available benzothiazole hydrazine and pyridyl phenyl ketone in refluxing methanol. Stereochemical implications for this compound are described.

Synthesis of isoflavones via base catalysed condensation reaction of deoxybenzoin

Base catalysed condensation reaction of o-hydroxyl-α-phenylacetophenones with formyl reagents affords various substituted isoflavones. Many bases were tested in the condensation reaction and DMAP was found to be the most effective catalysis.

ChemInform Abstract: Yb(OTf)3‐Catalyzed Condensation Reaction of β‐Naphthol and Aldehyde in Ionic Liquids: A Green Synthesis of Aryl‐14H‐dibenzo[a,j]xanthenes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Lipase-Catalyzed Synthesis of Aliphatic Poly(carbonate-co-esters)

Candida antarctica Lipase B (CALB) was found to catalyze condensation reactions of diethyl carbonate (DEC), diester, and diol to form aliphatic poly(carbonate-co-esters). Poly(butylene carbonate-co-butylene succinate), poly(BC-co-BS), and poly(hexamethylene carbonate-co-hexamethylene adipate), poly(HC-co-HA), with about 1:1 mol/mol ester-to-carbonate repeat units, were prepared by maintaining the diol/diester monomer feed ratio (mol/mol) at 2 to 1. By varying the [DEC] to [1,4-butanediol minus diethyl succinate] ratio from 1:1 to 4:1, poly(BC-co-BS) with terminal groups of up to 96 mol % hydroxyl and 90 mol % ethyl carbonate plus ethyl ester, respectively, were prepared. Weight-average molecular weights (Mw) of poly(BC-co-BS) and poly(HC-co-HA), without product fractionation, reached 26 000 and 59 000 at 80 and 90 °C, respectively. Low polydispersities of poly(HC-co-HA) (Mw/Mn ∼ 1.5) indicate that the polymerization proceeds with chain selectivity. NMR analysis revealed poly(BC-co-BS) copolymers contain carbonate and ester repeat units randomly distributed along polymer chains. CALB-catalyzed reactions between DEC and propyl propionate (PP) gave ethyl propionate (EP), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC). A reaction pathway to form these products was proposed to involve three equilibrium reactions for which equilibrium constants were determined. Furthermore, CALB-catalyzed carbonate−ester transacylation reactions at 95 °C, for 3 and ≥21 h, between poly(butylene carbonate) (PBC, Mw = 13 800) and poly(butylene succinate) (PBS, Mw = 23 400), gave block copolymers with an average segment length of 2.8 repeat units and random sequences, respectively.

Synthesis of 14‐{[(Un)substituted phenyl] or alkyl}‐14H‐dibenzo[a,j]xanthenes Using Yb(OTf)3 as an Efficient Catalyst under Solvent‐free Conditions

AbstractA series of 14‐{[(Un)substituted phenyl] or alkyl}‐14H‐dibenzo[a,j]xanthenes were prepared under solvent‐free conditions by Yb(OTf)3 catalyzed condensation reactions of β‐naphthol with various aldehydes. The process presented here is operationally simple, environmentally benign and has good to excellent yields. Furthermore, the catalyst can be recovered conveniently and reused efficiently.

ChemInform Abstract: Antimony(III) Sulfate Catalyzed Condensation Reaction of Indoles with Carbonyl Compounds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Yb(OTf) 3 catalyzed condensation reaction of β-naphthol and aldehyde in ionic liquids: a green synthesis of aryl-14 H-dibenzo[ a, j]xanthenes

A facile, efficient and green synthesis of aryl-14 H-dibenzo[ a, j]xanthenes has been developed by one-pot condensation of β-naphthol and substituted benzaldehydes in the presence of ytterbium triflates in ionic liquids.

Antimony(III) Sulfate Catalyzed Condensation Reaction of Indoles with Carbonyl Compounds

Antimony sulfate was found to be on effective catalyst for the condensation reaction of indoles with carbonyl compounds at room temperature. This catalyst is inexpensive, easily available and it was also found that this catalyst could be recovered quantitatively and reused without much loss of catalytic activity.

Efficient Condensation Reactions of Electron-Rich Arenes with Aldehydes and Enals Promoted by Gold(III) Chloride: Practical Synthesis of Triaryl- and Triheteroarylmethanes and Related Compounds

Electron-rich arenes undergo gold(III) catalyzed condensation reactions with aldehydes and enals to afford bis- and tris-addition products, respectively, in high yields.

Synthesis and Structure of 1-Substituted Benzopyrano- [4’,3’-c]benzo[3”,4”-ƒ]-2,8-dioxabicyclo[3.3.1]nonane

Abstract The base catalyzed condensation reaction between 4-hydroxycoumarin and 3-acetylcoumarin (3-benzoylcoumarin) in water at reflux led to the formation of 1-methyl (1-phenyl)- benzopyrano[4’,3’-c]-benzo[3”,4”-ƒ ]-2,8-dioxabicyclo[3.3.1]nonane (2a, b) as final products. When 4-hydroxycoumarin and 3-acetylcoumarin reacted in a glacial acetic acid in the presence of potassium acetate the final product was 7-[3-acetyl-2-oxo-3,4-dihydro-2H-[1]benzopyran-4-yl]methyl- 6H,14H,14bH-bis-([1]benzopyrano)[4,3-b:4’,3’-d]pyran-6,14-dione (4). 4-Hydroxycoumarin and 4-(5-bromo-2-hydroxyphenyl)-3-buten-2-one were condensed in water at reflux and 1- methylcoumarino-[4’,3’-c]-bromobenzo[3”,4”-ƒ ]-2,8-dioxabicyclo[3.3.1]nonane was a final product (3).

The stability of poly( m-carborane-siloxane) elastomers exposed to heat and gamma radiation

Poly( m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methylphenyl-silyl units were synthesised using the ferric chloride catalysed condensation reaction between di-chloro-diorganosilane and bis(di-methylmethoxysilyl)- m-carborane. These elastomeric materials were originally developed to have greater stability to extreme thermal environments and retain tailorable physical and chemical properties relative to comparable non-carborane containing elastomers. Prepared samples were aged either by heating in air at elevated temperatures or by gamma irradiation from a 60Co source. Multinuclear ( 1H, 13C and 11B) solid and solution state nuclear magnetic resonance (NMR) was used to assess degradation. This included measurements of segmental chain dynamics using a solid-echo pulse sequence reflecting changes in crosslink density and assessing changes to the carborane fragment by 11B and 1H Magic Angle Spinning (MAS) methods. Thermogravimetric measurements were also performed to assess thermal stability. Gamma radiation (to a dose of 1 MGy) was found to induce only a small degree of elastomer hardening as evidenced by a reduction in segmental chain dynamics. The carborane cage however, remained intact at these dose levels. Thermal degradation was observed to lead to oxidative crosslinking, the degree of which is dependent on temperature. At temperatures below 350 °C, only small changes in segmental dynamics were observed commensurate with only minor weight loss at this temperature. At temperatures above 350 °C, the degradation of the elastomer increased dramatically with decreased segmental dynamics and presumed partial oxidation of the carborane cage. The integrity of the m-carborane cage and the segmental dynamics were found to be significantly reduced at temperatures above 580 °C, in line with the known cage rearrangement temperature for icosahedral carboranes.

Crystal structure of stilbene synthase from Arachis hypogaea

Introduction. Stilbene synthase [STS; Enzyme Commission (EC) 2.3.1.95] and chalcone synthase (CHS; EC 2.3.1.74) are members of the type III polyketide synthases (PKSs) and plant-specific enzymes. 1 CHS is widely found in higher plants and plays a key role in the flavonoid biosynthesis by supplying chalcone to downstream enzymes. In contrast, a limited number of plants have STS essential for the synthesis of resveratrol utilized in the stilbenoid biosynthesis. 2 The members of CHS superfamily, including STS, produce linear polyketide intermediates by a common catalytic mechanism where coenzyme A (CoA)-linked starter molecules are iteratively condensed by acetyl units from malonyl-CoA. 3 STS and CHS share around 70% sequence identity without significant deletions and insertions; therefore, the enzymatic mechanism of STS has been considered to be very close to that of CHS. STS and CHS catalyze condensation reactions of pcoumaroyl-CoA and 3 acetyl units from malonyl-CoA, and produce a common linear tetraketide intermediate. In the following cyclization reaction, however, STS and CHS catalyze aldol and Claisen condensation of the tetraketide, resulting in 2 different final products, resveratrol and chalcone, respectively. The crystal structure and molecular mechanism of CHS from Medicago sativa (alfalfa) have recently been reported, 4 but the primary determinant of the cyclization reactions catalyzed by STS and CHS was not clear. More recently, the crystal structure of STS from Pinus silvestris (pine) was reported and provided a framework for understanding the specificity in the cyclization reaction. 5 This report describes the crystal structures of STS from Arachis hypogaea (peanut) in the absence and presence of its final product resveratrol at 2.4 A and 2.9 A, respectively. Detailed structural comparisons of STS from A. hypogaea (peanut STS) with STS from P. silvestris (pine STS) and CHS (alfalfa CHS) evidently revealed common differences between STS and CHS in the local conformation around the active site pocket.

A General Synthetic Approach to Novel Bis(tetracenyl) Aromatics for OFET Application

AbstractA molecular tool box is presented, allowing the efficient synthesis of a broad variety of bis(tetracenyl) aromatics. These materials might be of considerable interest as semiconductors in organic field-effect transistors. The general synthetic strategy applied here involves Diels-Alder reactions of bromobenzocyclobutene derivatives and arene-1,4-endoxides[1], followed by transition-metal catalyzed condensation reactions of the formed 9-bromo-6,11-dihydrotetracene derivatives with aryldiboronic and -stannyl derivatives, respectively. In the final step, the resulting bis(dihydrotetracenyl) derivatives were dehydrogenated, giving the bis(tetracenyl) aromatics in good yields. They were characterized using NMR, UV-vis and mass spectrometry. Moreover, for some of these semiconductors the charge carrier mobility in thin film transistors has been determined.

Highly Stable Polymers based on Poly(m -carboranyl-siloxane) Elastomers

ABSTRACTPoly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methyl(phenyl)-silyl units were synthesised using the Ferric Chloride catalysed condensation reaction between di-chloro-di-organosilane and 1, 7-bis(di-methyl(methoxy)silyl)-m-carborane. These prepared polymers were aged either by heating in air at elevated temperature or by λ-irradiation from a 60Co source. Multinuclear (1H, 13C and 11B) solid and solution state nuclear magnetic resonance was used to evaluate degradation. λ-irradiation doses to 1 MGy were found to induce only a small reduction in elastomer properties as evidenced by a reduction in segmental chain dynamics. Ageing at temperatures below 350°C similarly displayed a small reduction in segmental chain dynamics together and a concomitant weight loss as measured by differential scanning calorimetry. Above 350°C degradation of the elastomer was dramatic with a decreased segmental chain dynamics and oxidation of the carborane cage, vide infra.

An Efficient Procedure for the Synthesis of Diacetals from the Incl3·4H2O Catalysed Reaction of 2,2-bis (Hydroxymethyl)-1,3-Propanediol witH Aldehydes or Ketones

Diacetals of carbonyl compounds are synthesised in good yields by the InCl3·4H2O catalysed condensation reactions.

Enzyme-catalyzed condensation reaction in a mammalian alpha-amylase. High-resolution structural analysis of an enzyme-inhibitor complex.

Mammalian alpha-amylases catalyze the hydrolysis of alpha-linked glucose polymers according to a complex processive mechanism. We have determined the X-ray structures of porcine pancreatic alpha-amylase complexes with the smallest molecule of the trestatin family (acarviosine-glucose) which inhibits porcine pancreatic alpha-amylase and yet is not hydrolyzed by the enzyme. A structure analysis at 1.38 A resolution of this complex allowed for a clear identification of a genuine single hexasaccharide species composed of two alpha-1,4-linked original molecules bound to the active site of the enzyme. The structural results supported by mass spectrometry experiments provide evidence for an enzymatically catalyzed condensation reaction in the crystal.

Evidence for Catalytic Cysteine–Histidine Dyad in Chalcone Synthase

Chalcone and stilbene synthases (CHS and STS) catalyze condensation reactions of p-coumaroyl-CoA and three C2-units from malonyl-CoA, but catalyze different cyclization reactions to produce naringenin chalcone and resveratrol, respectively. Condensing activities of wild-type CHS and STS as well as STS-C60S mutant were inhibited by iodoacetamide (Idm) and diethyl pyrophosphate (DPC). DPC also inhibited malonyl-CoA decarboxylation activity of wild-type and C164S mutants of CHS and STS. Meanwhile, Idm treatment enhanced (two- to fourfold) malonyl decarboxylase activity of wild-type enzymes and STS-C60S, whereas this priming effect was not observed with C164S mutants of CHS and STS, indicating that the cysteine residue being modified by Idm is the catalytic Cys164 of CHS and STS. DPC inhibition of decarboxylation activity of wild-type CHS was pH-independent in the range of pH 5.8 to 7.8; however, its inhibitory effect on CHS-C164S increased as pH increased from 6.2 to 7.4 with a midpoint of 6.4. Based on the 3-D structure of CHS and the observed shift in microscopic pKa, it was concluded that the histidine residue being modified by DPC in CHS is likely the catalytic His303 and that His303 forms an ionic pair (catalytic dyad) with Cys164 in wild-type CHS. In addition, our results showed that Cys60 in STS is not essential for the activity and only a single cysteine (Cys164) participates in the catalysis as in CHS.

Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)methane]Mn(CO) 3}SO 3CF 3 complexes: comparison of ligand donor properties

The known ligands HC(pz) 3, HC(3,5-Me 2pz) 3, HC(3-Phpz) 3, and HC(3- t Bupz) 3 and the new ligand HC(3- i Prpz) 3 (pz=pyrazolyl ring) are prepared in CHCl 3–H 2O using the appropriate pyrazole, an excess of Na 2CO 3, and tetra- n-butylammonium bromide as the phase transfer catalyst. Using these conditions, good yields of the ligands are consistently obtained. The new ligand PhC(pz) 2py (py=pyridyl ring) is prepared in the CoCl 2 catalyzed condensation reaction of (pz) 2SO and Ph(py)CO. The reaction of HC(pz) 3, KO t Bu and para-formaldehyde followed by quenching with water yields HOCH 2C(pz) 3. All of these ligands, except HC(3- t Bupz) 3, react with [Mn(CO) 5]SO 3CF 3, prepared in situ from Mn(CO) 5Br and Ag(SO 3CF 3), to yield the respective [(ligand)Mn(CO) 3]SO 3CF 3 complex. The carbonyl stretching frequencies and 13C-NMR trends of these complexes indicate that the donor abilities of all of the ligands are fairly similar. The solid state structure of {[HC(3- i Prpz) 3]Mn(CO) 3} + shows the HC(3- i Prpz) 3 ligand is tridentate with the iso-propyl groups rotated away from the Mn(CO) 3 core of the cation relieving any possible steric congestion.

A theoretical exploratory study of low-energy (1–2 eV) electron catalysis in the [formula omitted] gas phase process

It is shown that electron capture by a reactant may catalyze condensation reactions that otherwise would require higher activation energies in the neutral state. Two competitive processes have been examined in the CO 2H 2 system: (a) CO 2 +H 2 → HCOOH , (b) CO+H 2O→HCOOH, of which only (a) is likely to occur through electron activation. Upon electron capture (threshold around 1 eV), bent hot CO 2 reacts with H 2 via a stepwise path, leading to formic acid with an overall activation energy close to 2 eV (neutral activation energy 3.17 eV). In the 2 eV energy range, a close contact {HCOO −⋯H •} complex is formed. After electron detachment, a diradical {HCOO • + H •} system results which spontaneously yields HCOOH. The electron is re-emitted with approximately its initial energy so that it can be regarded as a true catalyst for this reaction.

ChemInform Abstract: Synthesis of Fluorenebisphenoxy Derivatives by Acid‐Sulfur Compound Catalyzed Condensation Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.