Synthesis of a bicyclo[6.3.0]undecene skeleton characteristic of some cyclooctanoids by an intramolecular reductive coupling of carbonyls promoted by low-valent titanium

The synthesis of a bicycle[6.3.O]undecene skeleton characteristic of a number of cyclooctanoid natural products is described. The methodology applied relies on an intramolecular reductive coupling of a dialdehyde promoted by low valent titanium to construct the key eight-membered ring. The use of C8K-TiCl3 as an alternative process to the classical coupling developed by McMurry is presented. The dialdehyde 15, precursor of the bicyclo[6.3.0]undecene system, was constructed in a concise manner from 2-carbomethoxy-cyclopentanone in 5 steps with an overall yield of 40%. The key carbonyl coupling of dialdehyde 15 to produce the eight-membered ring proceeded in low yields (similar to 10%) despite several attempts to increase its efficiency.8327528

Palladium catalysed regioselective arylation of indoles, benzofuran and benzothiophene with aryldiazonium salts

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Aryldiazonium tetrafluoroborates have been successfully employed in the direct and regioselective arylation of heteroaromatics such as indole, benzofuran and benzothiophene. The cationic aryl palladium intermediates derived from the aryldiazonium salts act as effective electrophiles in the process. These arylating reactions display operational simplicity and provide the arylated heterocycles regioselectively in moderate to excellent yields.2311193011935Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

D,L-cis-2,3-pyrrolidine dicarboxylate alters [H-3]-L-glutamate binding and induces convulsions in mice

This study investigated whether D,L-cis-2,3-Pyrrolidine dicarboxylate (D,L-cis-2,3-PDC), a new glutamate analogue, alters glutamate binding to cerebral plasma membranes and whether N-methyl-D-aspartate (NMDA) receptors are involved in the convulsant effect of this compound. D,L-cis-2,3-PDC reduced sodium-independent [H-3]-L-glutamate binding to lysed membrane preparations from adult rat cortex and had no effect on sodium-dependent glutamate binding. Intracerebroventricular administration Of D,L-cis-2,3-PDC (7.5-25 nmol/5 mul) induced generalized tonic-clonic convulsions in mice in a dose-dependent manner. The coadministration of MK-801 (7 nmol/2.5 mul), with D,L-cis-2,3-PDC (16.5 nmol/2.5 mul), fully protected the animals against D,L-cis-2,3-PDC-induced convulsions, while the coadministration of DNQX (10 nmol/2.5 mul) increased the latency to convulsions but did not alter the percentage of animals that had convulsions. These results suggest that D,L-cis-2,3-PDC-induced effects are mediated predominantly by NMDA receptors. (C) 2003 Elsevier Inc. All rights reserved.76229529

Heck arylation of endocyclic enecarbamates with diazonium salts. Improvements and a concise enantioselective synthesis of (-)-codonopsinine

[GRAPHICS] Total enantioselective synthesis of the natural (-)-codonopsinine was accomplished in seven steps with an overall yield of similar to 16% starting from the five-membered endocyclic enecarbamate 4. The total synthesis features a highly efficient and stereoselective Heck arylation of endocyclic enecarbamate 4 with p-methoxybenzenediazonium tetrafluoroborate and a stereoselective epoxidation/epoxide opening sequence as key steps.2203039304

A TOTAL SYNTHESIS OF THE SESQUITERPENE QUINONE METACHROMIN-A

The first total synthesis of the marine natural product metachromin A was accomplished through a convergent synthesis amenable to the preparation of synthetic analogues. The main features of this synthesis are the introduction of the oxygenation at C-17 employing a Thiele acetoxylation reaction and a stereoselective Horner-Wadsworth-Emmons coupling3591367137

Heck arylations of N-acyl-3-pyrroline and N-acyl-1,2,5,6-tetrahydropyridine with aryldiazonium salts. Short syntheses of aryl gamma- and delta-lactams, baclofen, homobaclofen and analogues

Heck arylation of N-acyl-3-pyrrolines and an N-acyl-tetrahydropyridine with aryldiazonium tetrafluoroborates under phosphine-free conditions proceeded smoothly to give alpha-hydroxycarbamates (hemiaminals) or alpha-alkoxycarbamates which were oxidized to the desired gamma- and delta-lactams. Acidic hydrolysis of the gamma-lactams produced a series of arylated GABA derivatives, including baclofen, a useful therapeutic drug. in only three steps with ail overall yield of 63 76%, Starting from N-acyl-tetrahydropyridine, aryl-delta-lactams and higher homologues of baclofen can be obtained. (C) 2002 Elsevier Science Ltd. All rights reserved.43574174

Asymmetric synthesis of cis-2,4-disubstituted azetidin-3-ones from metal carbene chemistry

Several chiral cis-2,4-disubstituted azetidin-3-ones were prepared as single diastereoisomers from N-protected amino acids, employing a highly stereoselective copper carbenoid N-H insertion reaction of diazoketones. These azetidin-3-ones were then converted into fully substituted azetidines in a few steps in good to high yields. (c) 2005 Elsevier B.V. All rights reserved.69024-255636564

Stereoselective synthesis of the conformationally constrained glutamate analogue, (-)-(2R,3S)-cis-2-carboxyazetidine-3-acetic acid, from (S)-N-tosyl-2-phenylglycine

The stereoselective synthesis of a novel cis conformationally constrained glutamate analogue containing an azetidine framework was accomplished from (S)-N-tosyl-2-phenylglycine in moderate overall yield. The key steps in the synthesis involved a N-H carbenoid insertion promoted by Cu(acaC)(2), a very efficient Wittig olefination of an azetidin-3-one, followed by a highly stereoselective rhodium-catalyzed hydrogenation. Epimerization of the cis to the trans analogue was performed using DBU as base in toluene at reflux.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.101559156

Efficient synthesis of a new aminoazasugar and dihydroxyprolines from an endocyclic enecarbamate

A novel procedure for the synthesis of trans-2,3-(2-aminomethyl)-cis-3,4-dihydroxypyrrolidine (a new aminoazasugar) and cis-2,3- and trans-2,3-cis-3,4-dihydroxyprolines is presented. Starting from the known endocyclic enecarbamate 1-carbobenzyloxy-2-pyrroline, the above compounds were efficiently synthesized in 6 or 7 steps in good overall yields. In the key step, trans-2,3-(1-carbobenzyloxy)-cis-3,4-diacetyloxy-2-methoxypyrrolidine underwent Lewis acid promoted cyanation, presumably via the corresponding N-acyliminium ion.45122321232