Search results for "Chemical synthesi"
showing 10 items of 292 documents
Radiosynthesis of (±)-(2-((4-(2-[18F]fluoro-ethoxy)phenyl)bis(4-methoxy-phenyl)methoxy)ethylpiperidine-3-carboxylic acid: a potential GAT-3 PET ligan…
2001
A dysfunction of GABAergic neurotransmission is related to diseases such as epilepsy, Huntington-disease and Parkinson-syndrome. A new 18F-fluorine labelled GABA transporter ligand for the GABA-transporter subtype GAT-3 was developed which may allow the in vivo visualisation of GABAergic neurotransmission. The precursors ethyl (2-(4-hydroxyphenyl)bis(4-methoxyphenyl)-methoxy)ethyl)-piperidine-3-carboxylate and ethyl(2-((4-(2-tosylethoxy)phenyl)-bis(4-methoxyphenyl)-methoxy) ethyl)-piperidine3-carboxylate were synthesised and labelled by the use of 2-[18F]fluoroethyltosylate or [18F]fluoride. Subsequent cleavage of the ester moiety gave the final product (±)-(2-((4-(2-[18F]fluoroethoxy)pheny…
Chemoenzymatic-Chemical Synthesis of a (2-3)-Sialyl T Threonine Building Block and Its Application to the Synthesis of the N-Terminal Sequence of Leu…
2001
Protection of all functional groups of the carbohydrate portion of the chemoenzymatically synthesized sialyl T threonine ester 1 (R=R1 =H, R2 =tBu, Fmoc=9-fluorenylmethoxycarbonyl) and subsequent acidolysis of the tert-butyl ester afforded the building block 2 (R=Ac, R1 =Me, R2 =H). The latter is a useful tool in the solid-phase synthesis of the N-terminal sequence 3 of the leukemia-associated leukosialin.
Large Scale Synthesis of Mono- and Di-urethane Derivatives of Lysine.
1999
Orthogonally protected diurethane derivatives of lysine are valuable materials for peptide syntheses. An example is ZLys(Boc), which is exploited in the industrial production of certain well-established peptide drugs. 3,4) Another derivative is Fmoc-Lys(Boc), which is in common use in the laboratory synthesis of peptides. 5) The simplest route to these lysine derivatives seems to be using the copper complex for simultaneous protection of the a-amino and a-carboxyl function, N e -tert-butoxycarbonylation and then copper detachment. The obtained Lys(Boc) might be then subjected to N a -benzyloxycarbonylation.
Straightforward Stereoselective Access to Cyclic Peptidomimetics
2009
The preparation of cyclic dipeptide mimetics from chiral imino lactones derived from (R)-phenylglycinol is described. Key steps of the synthetic route included the fully stereoselective construction of a quaternary center, the formation of six-, seven-, or eight-membered lactams by means of an RCM cyclization, and the introduction of a new amino group within the lactam ring. The synthesis of a tripeptide mimetic is also reported.
Enzymatic glycosylation of o-glycopeptides
1992
Abstract O-Glycosylation of serine derivatives carried out with N-urethane protected glucosamine yields O-glycopeptides which are regio- and stereoselectively galactosylated with the aid of β-1,4-galactosyltransferase (EC 2.4.1.22).
Synthesis of brominated tetrathiafulvalenes via phosphite-mediated cross-coupling
2010
The synthesis of polybrominated tetrathiafulvalenes (TTF-Brn, 2-4) containing 2-4 bromine atoms via phosphite-mediated cross-coupling of bromo-substituted 1,3-dithiole-2-thiones and 1,3-dithiole-2-ones is reported. © 2010 Elsevier B.V.
Highly Diastereoselective Arylation of (S)-Mandelic Acid Enolate: Enantioselective Synthesis of Substituted (R)-3-Hydroxy-3-phenyloxindoles and (R)-B…
2005
An easy access to substituted (R)-3-hydroxy-3-phenyloxindoles, (R)-benzylic acids, and benzophenones is described. The reaction of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with several o- and p-halonitrobenzenes proceeds readily to give the corresponding arylation products in good yields and diastereoselectivities. The reduction of the nitro group with Zn/HCl/EtOH in the o-nitro arylation products with concomitant intramolecular aminolysis of the dioxolanone moiety leads directly to enantiomerically pure (R)-3-hydroxy-3-phenyloxindoles. On the other hand the basic hydrolysis of the dioxolanone moiety in all t…
Nucleophilic substitutions in the isoindole series as a valuable tool to synthesize derivatives with antitumor activity
2011
Abstract A novel synthetic approach to the synthesis of 3-substituted isoindoles through nucleophilic substitution of 3-halo derivatives by charged carbon, and neutral nitrogen, oxygen, and sulfur nucleophiles, assisted by a 1-acyl group, is reported. Aryl-thio-isoindoles, obtained through a direct nucleophilic substitution with sulfur nucleophiles, showed cytotoxic activity, with GI50 values from micromolar to sub-micromolar concentrations, against the total number of cell lines investigated.
Double Diastereoselection in Aldol Reactions Mediated by Dicyclohexylchloroborane between Chiral Aldehydes and a Chiral Ethyl Ketone Derived from l-E…
2005
Both matched and mismatched diastereoselections have been observed in the aldol reactions of a range of chiral aldehydes with the dicyclohexylboron enolate of a chiral ethyl ketone related to l-erythrulose. As was previously observed in the corresponding aldol reactions with l-erythrulose derivatives, the Felkin−Anh model provides an adequate explanation for the stereochemical outcome of reactions with chiral α-methyl aldehydes. However, a satisfactory account of the results observed with α-oxygenated aldehydes was only possible with the Cornforth model. As a practical application of the methodology described herein, a C1−C9 fragment of the structure of the antifungal macrolide soraphen A1α…
Stereoselective Synthesis of (+)-Boronolide
2002
The delta-lactone boronolide (+)-1, a pharmacologically active, naturally occurring product, has been synthesized in enantiopure form with L-erythrulose as the chiral starting material. The key steps of the synthesis were a highly stereoselective aldol-reduction one-pot sequence, an indium-mediated diastereoselective aldehyde allylation, and a ring-closing metathesis.