Search results for " Synthesis"

Diastereoselective Michael addition of (S)-mandelic acid enolate to 2-arylidene-1,3-diketones: enantioselective diversity-oriented synthesis of dense…

2006

[EN] A diversity-oriented approach to enantiomerically pure densely substituted pyrazoles, ¿-aryl-¿-pyrazolylatrolactic acid and ¿-aryl-¿-pyrazolylacetophenones has been developed. The approach utilises the conjugated addition of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde to several 2-arylidene-1,3-diketones, which proceeds readily to give the corresponding Michael adducts in good yields and diastereoselectivities. The cyclocondensation of the 1,3-diketone moieties present in Michael adducts with several hydrazines leads to enantiomerically pure densely substituted pyrazoles. Subsequent basic hydrolysis of the …

Classics in Total Synthesis. Targets, Strategies, Methods. VonK. C. Nicolaou und E. J. Sorensen. VCH, Weinheim, 1996. 798 S., geb./ Broschur 128.00 D…

1996

Novel synthesis of spherical MCM-48

1999

Abstract A novel synthesis route was developed for the cubic member of the M41S family, MCM-48, with a three-dimensional pore system allowing the formation of submicrometre- to micrometre-sized beads with a narrow pore-size distribution. The synthesis is based on the modified Stober method applying tetraethoxysilane, ethanol, water, ammonia and n -hexadecyltrimethylammonium bromide as template. The specific surface area, the specific pore volume and the average pore diameter were varied in the following ranges: 900–1600 m 2  g −1 , 0.5–0.9 cm 3  g −1 and 2–3 nm. Aluminium-, chromium-, gallium-, niobium- and vanadium-MCM-48 were also synthesized following this procedure.

ELECTROCHEMICAL CONVERSION OF DICHLOROACETIC ACID TO CHLOROACETIC ACID IN A MICROFLUIDIC STACK AND IN A SERIES OF MICROFLUIDIC REACTORS

2015

The electrochemical conversion of dichloroacetic acid to chloracetic acid was performed in three different micro devices: a simple micro fluidic cell; a microfluidic stack equipped with various electrode chambers in series and three micro fluidic cells in series. The electrochemical synthesis of chloracetic acid was performed successfully with high yields and selectivity under a single-pass mode without supporting electrolyte at low cell voltages. An increase of the productivity and of the final concentration of the target product was achieved by using a stack with two or three electrode chambers in series. The utilization of three micro reactors in series open interesting new perspectives,…

Enantioselective Synthesis of Cuparane Sesquiterpenes. Synthesis of (−)-Cuparene and (−)-δ-Cuparenol

1996

(−)-Cuparene and (−)-δ-cuparenol, two cuparane-type sesquiterpenoids, were synthesized from β-cyclogeraniol in 47% and 27% overall yield, respectively, using a Katsuki−Sharpless asymmetric epoxidat...

Heterogeneous vs Homogeneous Palladium Catalysts for Cross-Coupling Reactions

2012

A large number of immobilized-Pd-catalysts for cross-coupling reactions have been introduced in the last decade. Are the observed catalyzed reactions truly heterogeneous or are they homogeneous due to leached palladium? This account critically addresses the leaching issue by selectively referring to some of the newly developed catalytic systems in an attempt to evaluate said systems based on uniform criteria. The report is concluded by identifying the relevant chemical and structural challenges in the field.

Two chloride ions as a template in the formation of a cyclic hexaurea.

2006

Synthesis and radiosynthesis of N5-[18F]fluoroethyl-Pirenzepine and its metabolite N5-[18F]fluoroethyl-LS 75

2009

The well established M1 selective muscarinergic antagonist Pirenzepine 11-[2-(4-methyl-piperazin-1-yl)-acetyl]-5,11-dihydro-benzo[e]pyrido[3,2-b][1,4]diazepin-6-one (1) exhibits an unusual behaviour in vivo, which cannot be explained with M1 antagonism exclusively. One of the aspects discussed is a specific interaction with poly ADP-ribose polymerase (PARP-1). 1 undergoes metabolism to form LS 75 5,11-dihydro-benzo[e]pyrido[3,2-b][1,4]diazepin-6-one (2). In order to study deviations in Pirenzepine efficacy from pure M1 binding in vivo using PET, appropriate positron emitter labelled analogues of 1 and 2 were synthesised. Non-radioactive reference compounds 3 and 4 were tested for PARP-1 inh…

Enantioselective Synthesis of Unsymmetrical Benzoins from (S)-Mandelic Acid Enolate and Aromatic Aldehydes.

2004

The reaction of the lithium enolate of the 1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with aromatic aldehydes proceeds readily to give the corresponding aldol products in good yields and diastereoselectivities. Subsequent hydroxyl protection, basic hydrolysis of the dioxolanone, oxidative decarboxylation of the α-hydroxyacid moiety, and hydroxyl deprotection provides chiral unsymmetrical benzoins with high enantiomeric excesses.

Validation of the Tetracycline Regulatable Gene Expression System for the Study of the Pathogenesis of Infectious Disease

2011

Understanding the pathogenesis of infectious disease requires the examination and successful integration of parameters related to both microbial virulence and host responses. As a practical and powerful method to control microbial gene expression, including in vivo, the tetracycline-regulatable system has recently gained the favor of many investigative groups. However, some immunomodulatory effects of the tetracyclines, including doxycycline, could potentially limit its use to evaluate host responses during infection. Here we have used a well-established murine model of disseminated candidiasis, which is highly dependent on both the virulence displayed by the fungal cells and on the host im…