35217-21-1Relevant articles and documents
SYNTHESE ET REACTIVITE COMPAREE D'ALKOXY ET DE THIOALKOXYMETHYLENECETENES
Cheikh, A. Ben,Dhimane, H.,Pommelet, J.C.,Chuche, J.
, p. 5919 - 5922 (1988)
Heterosubstituted methyleneketenes 2d-g are obtained by flash-vacuum pyrolysis of Meldrum's acid derivatives 1d-g.The methoxymethyleneketene 2e is stable for a few hours at room temperature and gives 3e by dimerization; in contrast, the more reactive thiomethoxymethyleneketenes 2f-g are easily converted to 4f-g by intramolecular rearrangement.
Coordination of iron(III) cations to β-keto esters as studied by electrospray mass spectrometry: Implications for iron-catalyzed michael addition reactions
Trage, Claudia,Schroeder, Detlef,Schwarz, Helmut
, p. 619 - 627 (2005)
Solutions of FeIII salts and β-keto esters have been investigated by means of electrospray ionization mass spectrometry. The complexes formed in such solutions have been considered previously as active intermediates in FeIII-catalyzed Michael additions. By using different FeIII salts with a set of β-keto esters, cation and anion mass spectra were analyzed and the effects of ester concentration, the role of the counterion, and the structure of the ester employed are discussed. Depending on the basicity of the ester, an increase of its concentration may lead to a decrease in the concentration of iron complexes observed in the mass spectra. Counterions with strong binding affinities to iron are found to capture the metal as ferrates, thereby removing the metal from the catalytic cycle.
Synthesis of (-)-Flavoskyrins by Catalyst-Free Oxidation of (R)-Configured Dihydroanthracenones in Aqueous Media and Its (Bio)synthetic Implications
Mondal, Amit,De, Arijit,Husain, Syed Masood
supporting information, p. 8511 - 8515 (2020/11/12)
A catalyst-free method for the synthesis of dimeric (-)-flavoskyrins has been developed. It involves the autoxidation of chemoenzymatically synthesized (R)-configured dihydroanthracenones in the presence of molecular oxygen in buffer of pH 6.0 followed by spontaneous [4 + 2] cycloaddition in stereocontrolled exo-anti fashion to form (-)-flavoskyrins. The method is applied to obtain several homo- A s well as heterodimerized flavoskyrins (nine examples) in 27-72% yield and implies the involvement of a similar pathway in the (bio)synthesis of modified bisanthraquinones and their analogues.
Identification and characterization of an anthrol reductase from: Talaromyces islandicus (Penicillium islandicum) WF-38-12
Singh, Shailesh Kumar,Mondal, Amit,Saha, Nirmal,Husain, Syed Masood
supporting information, p. 6594 - 6599 (2019/12/26)
An NADPH-dependent oxidoreductase from Talaromyces islandicus WF-38-12 has been identified through genome analysis. It has been shown to catalyze a regio- and stereoselective reduction of anthrols (formed in situ by the reduction of anthraquinones in the presence of Na2S2O4) to (R)-dihydroanthracenones, with high enantiomeric excess (>99%). The implications of results on the biosynthesis of deoxygenated (bis)anthraquinones and modified (bis)anthraquinones are discussed.
First enantioselective total synthesis of altersolanol A
Mechsner, Bastian,Hen?en, Birgit,Pietruszka, J?rg
supporting information, p. 7674 - 7681 (2018/11/02)
The first enantioselective total synthesis of altersolanol A, a secondary metabolite from the endophytic fungi Stemphylium globuliferum and Alternaria solani, is described. The key step towards the tetrahydroanthraquinone core was an asymmetric Diels-Alder (D-A) cycloaddition promoted by (R)-3,3′-diphenyl-BINOL/boron Lewis acid with good to excellent yields and excellent diastereo- and enantioselectivity (>95 : 5 dr and 98 : 2 er).
Multifunctional Cyclopentadienes as a Scaffold for Combinatorial Bioorganometallics in [(η5-C5H2R1R2R3)M(CO)3] (M=Re, 99mTc) Piano-Stool Complexes
Frei, Angelo,Spingler, Bernhard,Alberto, Roger
supporting information, p. 10156 - 10164 (2018/07/29)
Multifunctional cyclopentadiene (Cp) ligands and their rhenium and 99mTc complexes were prepared by a versatile synthetic route. The properties of these Cp ligands can be tuned on demand, either during their synthesis (variation of R1) or through post-synthetic functionalization with two equal or different vectors (V1 and V2). Variation of these groups enables a combinatorial approach in the synthesis of bioorganometallic complexes. This is demonstrated by the preparation of Cp ligands containing both electron-donating and electron-withdrawing groups at the R1 position and their subsequent homo- or heterofunctionalization with biovector models (benzylamine and phenylalanine) under standard amide bond-formation conditions. All ligands can be coordinated to the fac-[Re(CO)3]+ and fac-[99mTc(CO)3]+ cores to give tetrafunctional complexes in straightforward and functional-group-tolerant procedures. The 99mTc complexes were prepared in one step, in 30 min, and under aqueous conditions from generator-eluted [99mTcO4]?.
Monomeric Dihydroanthraquinones: A Chemoenzymatic Approach and its (Bio)synthetic Implications for Bisanthraquinones
Saha, Nirmal,Mondal, Amit,Witte, Karina,Singh, Shailesh Kumar,Müller, Michael,Husain, Syed Masood
supporting information, p. 1283 - 1286 (2018/01/27)
Modified bisanthraquinones are complex dimeric natural products containing a cage-like structural motif. For their biosynthesis, monomeric dihydroanthraquinones have been proposed as key intermediates despite not being isolated from natural sources or synthesized as of yet. Here, isolation and characterization of dihydroemodin, as well as dihydrolunatin, synthesized by a biomimetic and chemoenzymatic approach using NADPH-dependent polyhydroxyanthracence reductase (PHAR) from Cochliobolus lunatus followed by Pb(OAc)4 oxidation is reported. Subsequent dimerization through a hetero-Diels–Alder reaction of the dihydroemodin and dihydrolunatin resulted in (?)-flavoskyrin (68 %) and (?)-lunaskyrin (62 %), respectively. Pyridine treatment of (?)-flavoskyrin and (?)-lunaskyrin gave (?)-rugulosin and (?)-2,2′-epi-cytoskyrin A in 64 % and 60 % yield, respectively, through a cascade that involves two dimeric intermediates. Implications of the described synthesis for the biosynthesis of bisanthraquinones by a combination of enzymatic and spontaneous steps are discussed.
An indium-promoted alternative to the knoevenagel condensation of aldehydes with methyl acetoacetate
Paquette, Leo A.,Kern, Benjamen E.,Mendez-Andino, Jose
, p. 4129 - 4132 (2007/10/03)
Addition of methyl (E)-4-bromo-3-methoxycrotonate to aldehydes in the presence of indium and water delivers β-hydroxy esters, acidic hydrolysis of which leads to Knoevenagel-like adducts.
Asymmetric Hetero-Diels-Alder Reaction of α-Alkoxy Aldehydes with Activated Dienes. The Scope of Lewis Acid Chelation-Controlled Cycloadditions
Midland, M. Mark,Koops, Roger W.
, p. 5058 - 5065 (2007/10/02)
The cycloaddition reactions of various α-alkoxy aldehydes with 1,3-dimethoxy-1--1,3-butadiene (Brassard's diene, 2) were performed under the Lewis acid catalysis of Eu(hfc)3, magnesium dibromide, or diethylaluminum chloride.Moderate to high diastereoselectivities were observed with Eu(hfc)3 and magnesium dibromide.Evidence from reactions of Eu(hfc)3 and magnesium dibromide catalysis indicated a possible "chelation-control" pathway.Lewis acid catalysis from diethylaluminum chloride provides products with moderate to high diastereoselectivity.The mechanistic pathway with catalysis by diethylaluminum chloride was less clear.A possible mechanism based upon a "Cram" addition is considered.
The Compounds Related to 3-(1-Imidazolyl)-2-alken-1-ones. Preparation and Reactions
Kashima, Choji,Tajima, Tadakuni,Omote, Yoshimori
, p. 171 - 176 (2007/10/02)
Compounds related to 3-(1-imidazolyl)-2-alken-1-ones, 3-(1-imidazolyl)-2-alkenoic acid derivatives and 2-alken-1-ones having heterocycles on the C-3 carbon were prepared.The reaction of nucleophiles with these compounds was also discussed.
