Herein, we describe how minor structural modifications to our bifunctional organocatalysts based on sugar amino acids (SAAs) can alter the network of non‐covalent interactions (NCIs) within catalyst, leading significant changes in their catalytic activity. This is attributed intra‐catalyst NCIs, which induce conformational that are reflected transition state rate‐determining step Michael addition aldehydes trans‐β‐nitrostyrenes. Through kinetic experiments, analysis, and DFT calculations,...

The first example of a regioselective and organocatalyzed 1,3-dipolar cycloaddition reaction between conjugated alkynoates nitrones "on water" is described.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCD and 1H NMR Study of the Rotational Population Dependence Hydroxymethyl Group in .beta. Glucopyranosides on Aglycon Its Absolute ConfigurationEzequiel Q. Morales, Juan I. Padron, Mar Trujillo, Jesus T. VazquezCite this: J. Org. Chem. 1995, 60, 8, 2537–2548Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April...

Water molecules confined inside narrow pores are of great importance in understanding the structure, stability, and function water channels. Here we report that besides H-bonding structures pore, permanent presence a significant, fast-moving fraction incompletely H-bonded pore should control free entry exit water. This is achieved by means complementary DSC solid-state NMR studies. We also present compelling evidence from X-ray diffraction data cluster formed six most stable cage-like...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTetra-O-benzoylglucosylation: A New 1H Nuclear Magnetic Resonance Method for Determination of the Absolute Configuration Secondary AlcoholsMar Trujillo, Ezequiel Q. Morales, and Jesus T. VazquezCite this: J. Org. Chem. 1994, 59, 22, 6637–6642Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November...

The rotational populations of the hydroxymethyl group in chiral and nonchiral alkyl α- β-galactopyranosides proved, on basis circular dichroism (CD) 1H NMR data, to be dependent structure aglycon: population gt tg rotamers increased decreased, respectively, as pKa bonded alcohol (aglycon) increased, while gg rotamer remained practically constant. Furthermore, low-temperature CD measurements proved that most stable is gt, not tg. In addition, a clear correlation between absolute configuration...

Abstract Cooperativity is one of the most relevant features displayed by biomolecules. Thus, challenges in field supramolecular chemistry to understand mechanisms underlying cooperative binding effects. Traditionally, cooperativity has been related multivalent receptors, but Williams et al. have proposed a different interpretation based on strengthening noncovalent interactions within receptors upon binding. According such an interpretation, positive operates through structural tightening....

Abstract New pyranoid ε‐sugar amino acids were designed as building blocks, in which the carboxylic acid and amine groups placed positions C2 C3 with respect to tetrahydropyran oxygen atom. By using standard solution‐phase coupling procedures, cyclic homooligomers containing synthesized. Conformation analysis was performed by NMR spectroscopic experiments, FTIR studies, X‐ray analysis, a theoretical conformation search. These studies reveal that presence of methoxy group position C4 pyran...

Primary amoebic meningoencephalitis (PAM) is a central nervous system (CNS) disease caused by Naegleria fowleri that mainly affects children and young adults with fatal consequences in most of the cases. Treatment protocols are based on combination different antimicrobial agents, nonetheless there need to develop new anti-Naegleria compounds low toxicity full effects compared currently used drug combination. The marine environment well-established source bioactive natural products. In this...

Abstract A new series of hybrid dipeptide‐like organocatalysts based on pyranoid ϵ ‐ or ζ‐amino acids and proline have been prepared for the asymmetric Michael addition aldehydes to β‐nitrostyrenes. The reaction proceeds under mild conditions afford a wide range γ‐nitroaldehydes with up 98% yield 96% ee . These dipeptides are bifunctional organocatalysts, at N‐terminus carboxylic acid C‐terminus. tetrahydropyran unit embedded in induces well‐defined conformation that is responsible...

Positive cooperativity between host conformational equilibria and guest binding has been widely reported in protein receptors. However, examples of this kind synthetic hosts are scarce largely serendipitous, among other things because it is hard to envision systems which display cooperativity. In order shed some light on the correlation free binding, selected structural modifications have performed over a family nonpreorganized induce changes analyze their effect affinity. The was evaluated...

The binding modes of a series molecules, containing the glucosamine (1→6) myo-inositol structural motif, into ATP site catalytic subunit cAMP-dependent protein kinase (PKA) have been analysed using molecular docking. These calculations predict that presence phosphate group at non-reducing end in pseudodisaccharide and pseudotrisaccharide structures properly orientate molecule present best shape complementarity. Therefore, pseudodisaccharides pseudotrisaccharides synthesised from common...

Naegleria fowleri is an opportunistic protozoan, belonging to the free-living amoeba group, that can be found in warm water bodies. It causative agent primary amoebic meningoencephalitis, a fulminant disease with rapid progression affects central nervous system. However, no 100% effective treatments are available and those currently used involve appearance of severe side effects, therefore, there urgent need find novel antiamoebic compounds low toxicity. In this study, vitro activity six...

Okadaic acid (OA) is a toxin responsible for diarrhetic shellfish poisoning and an extremely useful tool studying processes that are regulated by phosphorylation, although the exact mechanism of action still undetermined. We report on study proved existence OA in unusual dimeric form when complexed with potassium ion. The proposed structure this dimer based spectroscopic conformational studies.

Six dihydro-β-agarofuran [5,11-epoxy-5β,10α-eudesm-4(14)-ene] sesquiterpenes with a novel substitution pattern were isolated from Maytenus magellanica and their structures elucidated by means of 1H 13C NMR spectroscopic studies, including 1H–13C heteronuclear correlation (HETCOR), long range spectra inverse detection (HMBC) NOE experiments. Their absolute configurations determined application the CD exciton chirality method while hydrolysis preparation derivatives provided additional...

The unique solid-state hydration/dehydration properties of the diacid (±)-1e in comparison with other homologues same family are studied. Hydrophobic enhancement, which is a consequence loss water molecules from chains, property that can be exploited to achieve organic condensed systems for nonpolar by interstitial van der Waals confinement.

[reaction: see text] A convergent design for the preparation of a polyoxyethylene-based channel molecule is presented, and synthesis key unit 2 required projected construction described. The essential elements included face to oriented macrorings spaced by rigid trans-fused oxanes. strategy combines conformational predictability C-linked oxanyl systems ring-closing metathesis crown ethers with engineerable ion-binding abilities.

Abstract A time-sequential approach to study the hydration thermodynamics of designed organic compacts should prove useful in other cases where cavities are occupied by multiple water molecules, i. e. natural cell channels as aquaporins.