PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Biomimetics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources
PubMed2005

Biomimetic macrocycle-forming Diels-Alder reaction of an iminium dienophile: synthetic studies directed toward gymnodimine.

The macrocyclic core of gymnodimine has been constructed via an intramolecular Diels-Alder reaction of an alpha,beta-unsaturated iminium dienophile in water. The cycloaddition furnished a single exo-product, along with two endo-products. Through X-ray analysis of a suitable derivative, the stereochemistry of the exo-product was established, thereby demonstrating that its stereochemistry matches that of gymnodimine. In contrast, macrocyclization of an analogous alpha,beta-unsaturated ketone dienophile gave only undesired endo-products. Interestingly, the imine dienophile shows remarkable stability in water. [reaction: see text]

Crystallography, X-Ray↗
PubMed2006

Synthesis of (+)-sch 642305 by a biomimetic transannular Michael reaction.

[reaction: see text] The synthesis of (+)-Sch 642305 (1) has been completed in 17 steps in 1.6% overall yield. Transannular Michael reaction of 2b with NaH in THF provided cyclohexenone 23 stereospecifically. Heating 23 in TFA/CDCl(3) provided a 3:1 equilibrium mixture of 23 and 25, which was hydrolyzed to give (+)-6-epi-Sch 642305 (24) and (+)-Sch 642305 (1), respectively.

Macrolides↗
PubMed1999

A general route to 4-imidazolyl-containing multidentate ligands for biomimetic studies.

[formula: see text] 4-iodo-1-tritylimidazole undergoes magnesium-iodine exchange with a Grignard reagent to give selectively the 4-magnesioimidazole derivative, which reacts with esters to form a variety of poly-4-imidazolyl carbinol compounds in 40-79% yields. A wide range of bi-, tri-, and pentadentate ligands featuring 4-substituted imidazole units have been efficiently synthesized.

Imidazoles↗
PubMed1999

Catalysis and acceleration of acyl transfer by aminocyclodextrins: a biomimetic system of use in enzyme modeling and drug design.

[formula: see text] Aminocyclodextrins (ACDs), perfunctionalized at the 6-position with amino groups, bind phosphonoformate (PFA) diesters and accelerate acyl transfer reactions with high efficiency at neutral pH. Aminolysis and esterolysis are accelerated and hydrolysis of PFA diesters is catalyzed by ACDs. PFA diesters have significant antiviral activity. The rapid reactions observed with ACDs show that biological nucleophiles may undergo facile covalent modification by PFA esters at physiological pH, which has significant implications for prodrug and drug design strategies.

Catalysis↗
PubMed1999

Studies toward the biomimetic synthesis of tropolone natural products via a hetero Diels-Alder reaction.

Analogues of the tropolone natural products pycnidione and epolone B were synthesized via a hetero Diels-Alder reaction of benzotropolone 10 with humulene. The quinone methide benzotropolone 13 was generated in situ by thermalisation of benzotropolone 10. Benzotropolone 10 was derived from phthalic acid via carbonyl ylide 8a followed by an intramolecular 1,3-dipolar cycloaddition and subsequent acid-catalyzed ring opening.

Fungi↗
PubMed1997

Biomimetic metabolism of artelinic acid by chemical cytochrome P-450 model systems.

PURPOSE: To study the reaction of artelinic acid with chemical model systems of cytochrome P-450 as a means of obtaining authentic samples of the putative metabolites necessary for identification of the mammalian metabolites of artelinic acid. METHODS: Artelinic acid was reacted with different organic complexes of iron(II). The reaction products were isolated and characterized by NMR and thermospray mass spectroscopy. RESULTS: Five compounds which are putative metabolites of artelinic acid were isolated from these reactions and unambiguously identified, while the identity of two other compounds await final confirmation. CONCLUSIONS: Standards of possible metabolites of artelinic acid can be produced by the reaction of the compound with ferrous complexes that may simulate cytochrome P-450 catalyzed metabolism of xenobiotics. This approach may provide a simple and versatile method for the formation of metabolites of artemisinin compounds which is more advantageous than previous approaches with fungal-based systems.

Antimalarials↗
PubMed1999

Proton speciation and microspeciation of vinpocetine and related compounds in aqueous and biomimetic media.

PURPOSE: The determination of protonation macroconstants of twelve compounds in the vincamine drug family and the determination of protonation microconstants of cis- and trans-apovincaminic acid in media of various solvent composition to characterise their site-specific basicity and to estimate the concentration of the membrane-penetrating and receptor-binding forms. METHODS: UV-pH titrations have been used to determine the protonation macroconstants in 10-43 wt% methanol/water mixtures. Yasuda-Shedlovsky extrapolation was applied to obtain aqueous logK values for compounds sparingly soluble in water. Protonation microconstants were also determined by deductive methods for compounds of free carboxylic group. RESULTS: In the case of the two water-soluble compounds the extrapolated and the directly measured aqueous logK values were in good agreement, verifying all other extrapolated data. Compounds of cis-D/E ring anellation are 0.4-0.8 logK units more basic than their epimeric, trans counterparts. The pH-dependent distribution of apovin-caminic acid microspecies in aqueous and membrane-like media is depicted in microspeciation diagrams. CONCLUSIONS: The N(4) nitrogen is more shielded by the adjacent ethyl group in trans-D/E ring anellation eburnanes than in cis ones, as reflected by the protonation constants. Solvent-dependent basicity data predict superiority of trans isomers in lipophilicity and membrane-penetrating ability.

Hydrogen-Ion Concentration↗
PubMed2002

Cell adhesion and proliferation on biomimetic calcium-phosphate coatings produced by a sodium silicate gel methodology.

The present study describes a methodology to produce bioactive coatings on the surface of starch based biodegradable polymers or other polymeric biomaterials. As an alternative to the more typical bioactive glass percursors, a sodium silicate gel is being employed as a nucleating agent, for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as bone tissue engineering scaffolds. This treatment is also very effective in reducing the incubation periods, being possible to observe the formation of an apatite-like layer, only after 6 h of immersion in a simulated body fluid (SBF). The influence of the SBF concentration on the formation of the apatite coating was also studied. The apatite coatings formed under different conditions were analyzed and compared in terms of morphology, chemical composition and structure. After the first days of SBF immersion, the apatite-like films exhibit the typical cauliflower like morphology. With increasing immersion times, these films exhibited a partially amorphous nature and the Ca/P ratios became very closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for pre-calcifying bone tissue engineering scaffolds. Therefore, in order to study cell behavior and response to these apatite coatings, adhesion, morphology, and proliferation of a human osteoblast cell line (SaOS-2) was also analyzed after being cultured in the coatings formed after 15 days of immersion in SBF. Results indicate a good correlation between crystallinity of the apatite like coatings formed in these conditions and respective cell spreading and morphology. In general, higher cell proliferation was observed for higher crystalline Ca-P coatings.

Journal Article↗
PubMed2003

Biomimetic studies on polyenes.

The crispatenes and SNF4435 C&D are complex polypropionate derived natural products. The core structures of these compounds along with a complex unnatural structure can be easily prepared from a common polyene precursor simply by variation of the reaction conditions. The reaction pathways provide insight into the biosynthesis of these complex natural products.

Magnetic Resonance Spectroscopy↗