Solid-phase synthesis of 2β-methyl substituted penam derivatives through penicillin sulfoxide rearrangement

A new, robust protocol for the solid-phase synthesis of 2β-methyl substituted penam derivatives is described. This synthetic sequence works reliably in good to high overall yields using Merrifield resin as support. The key step involves the thermal rearrangement of the corresponding penicillin sulfoxide.     

Synthesis of 3β-methyl ether of dehydroepiandrosterone by biotransformation of 3β-methyl ether of cholesterol with cells of mycobacteria Mycobacterium sp.

Russian Chemical Bulletin - 3p-Methyl ether of dehydroepiandrosterone was obtained by microbiological transformation of 3ß-methyl ether of cholesterol with Mycobacterium sp....     

Convenient Method for the 3‐Functionalization of Isoindazoles

The C‐3 position of isoindazoles is readily functionalized by metalation with lithium diisopropylamide followed by reaction with a variety of electrophiles.     

Carbene-Catalyzed Direct Functionalization of the β-sp3-Carbon Atoms of α-Chloroaldehydes

A direct functionalization of the β-sp³ carbon atom of α-chloro aldehyde has been developed. The reaction starts with the addition of a carbene catalyst to α-chloroaldehyde to eventually form the homoenolate intermediate. This overall redox-neutral process successfully converts the otherwise inert β-sp³-carbon atom of the aldehyde substrate to a nucleophilic carbon atom for asymmetric reactions. This study constitutes the first success in activating α-chloroaldehydes to generate homoenolate intermediates by carbene organic catalysis and shall encourage further explorations in using organic catalysis for transforming inert chemical bonds.     

Dissection of the difference between the group I metal ions in inhibiting GSK3β: a computational study

Glycogen synthase kinase 3β (GSK3β) is a serine/threonine kinase that requires two cofactor Mg(2+) ions for catalysis in regulating many important cellular signals. Experimentally, Li(+) is a competitive inhibitor of GSK3β relative to Mg(2+), while this mechanism is not experienced with other group I metal ions. Herein, we use native Mg(2)(2+)-Mg(1)(2+) GSK3β and its Mg(2)(2+)-M(1)(+) (M = Li, Na, K, and Rb) derivatives to investigate the effect of metal ion substitution on the mechanism of inhibition through two-layer ONIOM-based quantum mechanics/molecular mechanics (QM/MM) calculations and molecular dynamics (MD) simulations. The results of ONIOM calculations elucidate that the interaction of Na(+), K(+), and Rb(+) with ATP is weaker compared to that of Mg(2+) and Li(+) with ATP, and the critical triphosphate moiety of ATP undergoes a large conformational change in the Na(+), K(+), and Rb(+) substituted systems. As a result, the three metal ions (Na(+), K(+), and Rb(+)) are not stable and depart from the active site, while Mg(2+) and Li(+) can stabilize in the active site, evident in MD simulations. Comparisons of Mg(2)(2+)-Mg(1)(2+) and Mg(2)(2+)-Li(1)(+) systems reveal that the inline phosphor-transfer of ATP and the two conserved hydrogen bonds between Lys85 and ATP, together with the electrostatic potential at the Li(1)(+) site, are disrupted in the Mg(2)(2+)-Li(1)(+) system. These computational results highlight the possible mechanism why Li(+) inhibits GSK3β.     

Functionalization of the cluster [FeCp(μ3–CO)]4

The 33-year-old cluster [FeCp(μ₃-CO)]₄ (1) has been functionalized by reaction with lithium diisopropylamide, followed by CO₂, to give the acid RCO₂H, 2 (R=Fe₄(μ₃–CO)₄Cp₃(C₅H₄–)), recently reported by Rauchfuss. The cluster 2 reacts with (CO)₂Cl₂ to give the new cluster RCOCl (3), which reacts with the disulfide {S(CH₂)₁₁NH₃⁺Cl^–}₂ to give the amido-cluster disulfide [Fe₄(μ₃–CO)₄Cp₃{η⁵′-C₅H₄C(O)NH(CH₂)₁₁S}]₂ (4), with NEt₃ to give the diethylamido cluster [Fe₄Cp₃(η⁵-C₅H₄CONEt₂)(μ₃-CO)₄] (5), and with N-hydroxysuccinimide to give the N-succinimidyl ester cluster 6. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAScluster functionalization / tetrairon-cylopentadienyl-carbonyl cluster     

Functionalization of the Allyl Fragment in (+)-δ-Cadinol

Epoxidation, bromination, and iodination of the double bond in (+)--cadinol under various conditions are accompanied by formation of 1,4- or 1,5-epoxy derivatives. By contrast, vicinal hydroxylation gives rise to normal products. Intramolecular cyclization of the resulting vicinal diols was studied.     

Influence of α-methyl substitution of proline-based organocatalysts on the asymmetric α-oxidation of aldehydes

The direct asymmetric organocatalytic α-oxidation of aldehydes using trans-2-(p-methylphenylsulfonyl)-3-phenyloxaziridine is reported. This method affords the S isomer of α-hydroxy aldehydes, thereby complementing the selectivity for the R isomer observed using the two-step nitrosobenzene method. Use of α-methylproline and α-methylproline tetrazole significantly increases the enantioselectivity observed for the α-oxidation of aldehydes compared to analogous unsubstituted organocatalysts.     

Study on the Synthesis of Di(3,4-methyl) Benzylidene Sorbitol

Di (3,4-methyl) benzylidene sorbitol (briefly referred as “ DMDBS ”), used as transparency nucleating agent in crystallinity polyolefin kind resin, can dramaticly reduce the haze of plastic products, improving their quality in transparency, resin’s rigidity, heat resistant temperature and modulus of bending. DMDBS, having these characteristics, has been widely used as polyolefin processing auxiliary. With the presence of hydrophobicity organic solvent and lower alcohol, the nucleating ag…     

Basic Functionalization of Hexagonal Mesoporous Silica

Recently, a novel method of modification, i.e., functionalizing the internal surface of mesoporous materials has been reported1-5, owing to the large pore size, the silanol groups, which are in a big population in mesoporous materials, can chemically couple with the active groups of some bulky organic functional molecules. Based on this approach, one can obtain novel solid basic catalysts. Here we functionalized the hexagonal and hexagonal-like mesoporous silica materials SBA-3 and HMS wi…     

Functionalization of the Methyl C(sp3)–H Bond of 2,3-Dimethylquinoxaline with 5-Arylfuran-2,3-diones

Russian Journal of Organic Chemistry - 5-Arylfuran-2,3-diones reacted with 2,3-dimethylquinoxaline to give mono- and bis-C-acylation products,...     

Static sterochemistry of the β-diketonate complexes of group II metals

The static sterochemistry in solution of the β-diketonate complexes of Be, Mg, Ca, Ba and Zn was investigated using ¹H-NMR techniques. It was ascertained that the bis-acetylacetonate complexes of Mg, Ca and Ba are polymeric in solution, in contrast to the dipivaloylmethanate complexes of Mg and Zn which are monomeric in solution. The benzoylacetonate chelates of all the metals studied were found also to be monomeric in solution. Chemical shift values and other arguments led us to favor a pseudo-tetrahedral D_2d idealized structure for all the complexes investigated.     

Functionalization of Testosterone at Position 7α and Synthesis of 7α-(3-Methoxypropyl)-4-androsten-17β-ol-3-one

An efficient transformation of the terminal alkene function of 7α-allyltestosterone is reported along with the stereospecific synthesis of 7α-(3-methoxypropyl)-4-androsten-17β-ol-3-one.     

Gold-Catalyzed C−H Functionalization Polycondensation for the Synthesis of Aromatic Polymers

Homogeneous gold (Au) complexes have demonstrated tremendous utility in modern organic chemistry; however, their application for the synthesis of polymers remains rare. Herein, we demonstrate the first catalytic application of Au complexes toward the polycondensation of alkyne-containing comonomers and heteroarene nucleophiles. Polymerization occurs through successive intermolecular hydroarylation reactions to produce high molecular weight aromatic copolymers with 1,1-disubstituted alkene backbone linkages. Clear correlations between the rate and degree of polymerization (DP) were established based on catalyst structure and counterion pairing, thus enabling polymerization reactions that proceeded with remarkable efficiency, high reactivity, and exceptional DPs. The reactivity is broad in scope, enabling the copolymerization of highly functionalized aromatic and aliphatic monomers. These results highlight the untapped utility of Au catalysis in providing access to new macromolecular constructs.     

Rearrangement reaction of the hydroxyl group of ω-hydroxy-alkyltriphenyl phosphonium bromides

No molecular ion peak from the Electron Impact lonization of eight co-hydroxyalkyltriphenyl phosphonium bromides(Ph3P (CH2)nOHBr-,n=2-6,8-10)can be found,except a part of some relative powerful fragment ions can be observed only.Each compound forms a very characteristic ion(O=PPbj-1) at m/z 277 through hydroxyl rearrangement reaction.The intensity of this ion is closely related with the size of the carbon chain of hydroxyalkyl and with temperature of ion source and temperature of sample probe.The above rearrangement reaction and the reaction to form ion at m/z 262 take place simultaneously,thus leading to strong competition.At n=2,ion at m/z 277 is the most powerful and becomes continuously the base peak.At n=3 and n=4,the intensity of ion at m/z 262 reaches the maximum,and is always the base peak,and the relative abundance of m/z 277 is only around 2%.At n=5,6,8,9,10,m/z 277 becomes base peak when the temperature of probe is below 300℃.But,when the temperature increases from 300℃to 350℃,m/z 262 sud     

Electro-Olefination—A Catalyst Free Stereoconvergent Strategy for the Functionalization of Alkenes

Conventional methods carrying out C(sp²)−C(sp²) bond formations are typically mediated by transition-metal-based catalysts. Herein, we conceptualize a complementary avenue to access such bonds by exploiting the potential of electrochemistry in combination with organoboron chemistry. We demonstrate a transition metal catalyst-free electrocoupling between (hetero)aryls and alkenes through readily available alkenyl-tri(hetero)aryl borate salts (ATBs) in a stereoconvergent fashion. This unprecedented transformation was investigated theoretically and experimentally and led to a library of functionalized alkenes. The concept was then carried further and applied to the synthesis of the natural product pinosylvin and the derivatization of the steroidal dehydroepiandrosterone (DHEA) scaffold.     

Organometallic Approach to the Functionalization of Alkyl Groups Containing 1‐Phenylpyrroles

Novel regioselective methods have been developed for the mono‐ and difunctionalization of alkyl groups containing 1‐phenylpyrroles using different organometallic reagents. Tailoring the reagents and conditions allowed us to prepare several new mono‐ and rotationally restricted dicarboxylic acid derivatives of 1‐(alkylphenyl)pyrroles in good yields.     

Frequency assignment of the infrared and Raman spectra of β-methyl methylcrotonate and deuterated analogs

The i.r. and Raman spectra of β-methyl rnethylcrotonate and three deuterated derivatives have been investigated. Frequency assignments have been made based on band contours in the i.r. vapour spectra, depolarization ratios of the Raman lines, comparison with similar compounds and normal coordinate calculations.