A convergent, organocatalytic asymmetric aminomethylation of α,β-unsaturated aldehydes by N-heterocyclic carbene (NHC) and (in situ generated) Brønsted acid cooperative catalysis is disclosed. The catalytically generated conjugated acid from the base plays dual roles in promoting the formation of azolium enolate intermediate, formaldehyde-derived iminium ion (as an electrophilic reactant), and ...

In 1980 Rostislav Grigorchuk constructed a groupG of intermediate growth, and later obtained the following estimates on its growth γ [Gri84]: e √ n γ(n) en β , where β = log32(31) ≈ 0.991. Using elementary methods we improve the upper bound to γ(n) en α , where η ≈ 0.811 is the real root of the polynomial X + X + X − 2 and α = log(2)/ log(2/η) ≈ 0.767.

Catalytic intramolecular hydrofunctionalization of allylphenols to heterocyclic compounds mediated by rhodium(iii) porphyrin complexes was described. The Wacker-type intermediate β-heterocyclic alkyl rhodium complex was independently synthesized and crystallized.

We study the fourth-order nonlinear differential equation ` p(t)|x′′(t)|α−1 x′′(t) ́′′ + q(t)|x(t)|β−1 x(t) = 0, α > β, with regularly varying coefficient p, q satisfying Z ∞ a t “ t p(t) ”1/α dt <∞. in the framework of regular variation. It is shown that complete information can be acquired about the existence of all possible intermediate regularly varying solutions and their accurate asymptoti...

α,β-Unsaturated carboxylic acids undergo Rh(III)-catalyzed decarboxylative coupling with α,β-unsaturated O-pivaloyl oximes to provide substituted pyridines in good yield. The carboxylic acid, which is removed by decarboxylation, serves as a traceless activating group, giving 5-substituted pyridines with very high levels of regioselectivity. Mechanistic studies rule out a picolinic acid intermed...

Aggregation of polyglutamine peptides with β-sheet structures is related to some important neurodegenerative diseases such as Huntington's disease. However, it is not clear how polyglutamine peptides form the β-sheets and aggregate. To understand this problem, we performed all-atom replica-exchange molecular dynamics simulations of one and two polyglutamine peptides with 10 glutamine residues i...

A Cedecea davisae isolate, which was intermediate or resistant to third-generation cephalosporins and carbapenems, was recovered from a urine sample. Susceptibility testing, isoelectric focusing, and analysis of outer membrane proteins showed that AmpC β-lactamase expression combined with porin deficiency accounted for the carbapenem resistance. A cloning experiment followed by phenotypic and e...

A suitably protected Orn-derived (3S,4S)-β-lactam was used as common intermediate in the synthesis of conformationally constrained (3S,4S)-2-oxoazepane α,α- and (2S,3S)-2-oxopiperidine-β(2,3,3)-amino acid derivatives. Compared to alternative procedures using an N-p-methoxybenzyl group at the 2-azetidinone, the incorporation of a p-methoxyphenyl moiety is crucial for the excellent stereochemical...

The hormones secreted by intermediate lobe or middle lobe of pituitary gland are called melanocyte stimulating hormones or MSH. POMC is the precursor molecule which is cleaved by proteases to give ACTH and β-lipotropin. The ACHT is further cleaved to β-MSH which has 13 amino acids. There is also α-MSH which is present in larger quantities. Amino acids 11-17 of β-MSH are common to both α-MSH and...