Search results for "MIM"

Design of bioactive and structurally well-defined peptides from conformationally restricted libraries

2004

Libraries of peptides and proteins can be categorized according to the function of their origin in gene- and synthetic-based libraries. Both kinds of libraries have the potential to generate the same grade of molecular diversity, although the limits imposed by the synthetic methods have been lately a matter of discussion. However, the use of synthetic strategies allows incorporation of non-natural amino acids. The development of canfonnallonally restricted synthetic peptide libraries can be considered as a point of convergence of the two methodologies. In these libraries the diversity is grafted into scaffolds that are defined by stable secondary structural motifs, and the deconvolution pro…

Pleiotropic Role of Recombinant Silaffin-Like Cationic Polypeptide P5S3: Peptide-Induced Silicic Acid Stabilization, Silica Formation and Inhibition …

2016

Silica-mineralizing organisms such as diatoms manage several aspects of silica chemistry when polymerizing monomeric silicic acid into amorphous silica. Silicic acid is undersaturated in the diatoms’ habitats and mechanisms of enrichment and prevention of uncontrolled mineralization are not well understood. Diatom-biosilica is associated with organic compounds, including polycationic, post-translationally modified peptides termed silaffins, which induce the condensation of silicic acid under supersaturated conditions. Here, we report the pleiotropic action of the designed silaffin-like peptide P5S3, which (i) stabilizes 4–8x silicic acid (in supersaturated conditions of 8.3 mm), (ii) decele…

Chiral synthetic pseudopeptidic derivatives as triplet excited state quenchers

2009

The behavior of 6 pseudopeptidic models, synthesized by connecting different protected amino acids (Trp, Tyr, Phe, and Lys) with various diamino spacers, as quenchers of the triplet excited state of tiaprofenic acid (and its methyl ester), has been investigated. A series of quenching constants have been determined, which depend on the nature of the quencher and on the stereochemistry of the excited drug. A significant degree of stereodifferentiation has been found for the peptidomimetic synthesized with Phe and Tyr linked by a piperazine bridge. The obtained results support the utility of laser flash photolysis (LFP) as a tool to investigate the interactions between photoexcited drugs and s…

Solid Phases as Protective Environments for Biomimetic Catalysts

2014

Mimonoside D: a new triterpenoid saponin from Mimosa diplotricha Sauvalle (Fabaceae)

2021

A new triterpenoid saponin (Mimonoside D: 3-O-��-L-arabinopyranosyl-3��-hydroxyolean-12-en-28-oic acid 28-O-��-D-xylopyranosyl-(1���2)-��-D- glucopyranoside ester (1)) was isolated from the aerial parts of Mimosa diplotricha Sauvalle together with nine known compounds: 7,4���-dihydroxyflavone (2), kaempferol (3), lupeol (4), betulinic acid (5), ��-sitosterol (6), ��-sitosterol-3-O-��-D-glucopyranoside (7), lutein (8), 5,2���-dihydroxy-7,4���,5���-trimethoxyflavone (9) and vitexin (10). Their structures were elucidated on the basis of spectroscopic (1 D and 2 D nuclear magnetic resonance) and high-resolution mass spectrometric data as well as by comparison of their spectral data with those o…

Carbohydrates as Polyfunctional Scaffolds in Combinatorial Synthesis

2006

Carbohydrates are inexpensive, polyfunctional molecules which contain a high density of stereogenic centers. Taking advantage of these particular properties monosaccharides like glucose or mannose have been used for the construction of peptidomimetics which simulate recognition sites of somatostatin or RGD ligands of integrins. Due to their poly functionality, carbohydrates are considered promising scaffolds for combinatorial syntheses either in solution or on solid phase. The application of carbohydrate scaffolds, however, requires sets of orthogonally stable, selectively removable protecting groups, and the challenge in this combinatorial strategy increases with increasing number of hydro…

Co(II)-mediated synthesis of 2-carbamimidoylbenzoates and isoindole-1,3-diaminates

2015

Abstract Phthalonitrile, acetoxime and cobalt(II) nitrate hexahydrate are combined in acetone with formation of stable and easy to handle Co(II) complex [Co{C6H4C(NH2)NC(ONCMe2)2}2](NO3)2 (1). Interaction of 1 with excess alcohols ROH (also used as solvents) and 2 equiv of (NH4)2S leads, in one-step, to alkyl 2-carbamimidoylbenzoate nitrates [C6H4COOR{2-C(NH2)2}]NO3 [R=CH3, C2H5, C3H7, CH(CH3)2]. Similarly, N1,N3-dialkyl-1H-isoindole-1,3-diaminate nitrates [C6H4C(NR′)NC(NR′)]NO3 [R=C3H7, C4H9, C(CH3)3, CH2CH2OH, CH2CH2SC2H5) can be directly produced from 1 by its reaction with 4 equiv of amines and 2 equiv of (NH4)2S in alcoholic media.

An Approach to 2,4-Substituted Pyrazolo[1,5-a]pyridines and Pyrazolo[1,5-a]azepines by Ring-Closing Metathesis

2013

The ring-closing metathesis (RCM) reactions of dienylpyrazoles have been employed in the synthesis of pyrazolo[1,5-a]pyridine and pyrazolo[1,5-a]azepine derivatives. Based on this approach, the diastereoselective synthesis of potential peptidomimetics containing four amino acid residues with the second (i+1) and third (i+2) fragments having been substituted by bicyclic frameworks is described.

Back Cover: A Regio- and Diastereoselective Anodic Aryl-Aryl Coupling in the Biomimetic Total Synthesis of (−)-Thebaine (Angew. Chem. Int. Ed. 34/201…

2018

Increased conformational rigidity of humic substances by oxidative biomimetic catalysis

2005

A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed …