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Results for “Cyclopentanes”

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At least 91 records · Page 5Linked to original sources
PubMed1994

(+-)-1-Amino-1,3-cyclopentane-trans-dicarboxylic acid (trans-ACPD) induced inositol triphosphoric acid formation in the brain of iron-induced epileptic rats and epileptic El mice.

Myo-inositol-1,4,5-triphosphoric acid (IP3) formation stimulated by (+-)-1-amino-1,3-cyclopentane-trans-dicarboxylic acid (trans-ACPD) was examined in the cortex, hippocampus and cerebellum of iron-induced epileptic rats and epileptic El mice. Increased IP3 formation by trans-ACPD was observed in the cortex, hippocampus and cerebellum of iron-injected rats while it was found in the hippocampus and cerebellum of the saline-injected control rats. Increased IP3 formation by trans-ACPD was remarkably higher in the hippocampus of iron-injected rats than the other regions. Increased IP3 formation by trans-ACPD was observed in the cortex, hippocampus and cerebellum of ddY mice, while such an increase was found only in the cerebral cortex and not in the hippocampus and cerebellum of El mice. These findings suggest that the inositol response may be involved in the seizure mechanisms of iron-induced epileptic rats and epileptic El mice in some different forms.

Animals↗
PubMed2001

Characterization of an influenza A (H3N2) virus resistant to the cyclopentane neuraminidase inhibitor RWJ-270201.

The novel influenza virus neuraminidase (NA) inhibitor, (1S,2S,3R,4R)-3-[(1S)-(acetylamino)-2-ethylbutyl]-4-[(aminoiminomethyl)amino]-2-hydroxy-cyclopentanecarboxylic acid (RWJ-270201, BCX-1812), is a potent inhibitor of influenza A and B viruses in cell culture and in infected mice. A mouse-adapted strain of influenza A/Shangdong/09/93 (H3N2) virus was serially passaged in the presence of 1 microM compound. After the fourth passage, breakthrough of resistant virus occurred. By the tenth passage, a twice plaque purified isolate was obtained which could replicate in 10 microM inhibitor. The 50% effective concentration (EC(50)) values for RWJ-270201 against wild-type and resistant viruses, determined by using a cytopathic effect inhibition assay, were 0.007 and 23 microM, respectively. Cross-resistance to zanamivir and oseltamivir carboxylate was observed. The hemagglutinin (HA) and NA genes of the virus were sequenced to determine the mutation(s) which conferred drug resistance. No differences were found between the resistant and wild-type viruses in the NA gene. However, a point mutation resulting in a single amino acid change (Lys189Glu) was found in the resistant viral HA. The wild-type and resistant viruses were compared for virulence in BALB/c mice. The resistant virus was approximately tenfold less virulent than the wild-type virus based upon virus challenge dose. Mice infected with a lethal dose of the resistant virus could still be effectively treated with RWJ-270201. Thus, the HA mutation may allow for the spread of the virus in cell culture in the presence of the NA inhibitor, but not in mice.

Acids, Carbocyclic↗
PubMed2001

Catalytic asymmetric ring-opening metathesis/cross metathesis (AROM/CM) reactions. Mechanism and application to enantioselective synthesis of functionalized cyclopentanes.

Studies regarding the first examples of catalytic asymmetric ring-opening metathesis (AROM) reactions are detailed. This enantioselective cleavage of norbornyl alkenes is followed by an intermolecular cross metathesis with a terminal olefin partner; judicious selection of olefin is required so that oligomerization and dimerization side products are avoided. Results outlined herein suggest that the presence of suitably positioned heteroatom substituents may be critical to reaction efficiency. Mo-catalyzed tandem AROM/CM affords functionalized cyclopentyl dienes in >98% ee and >98% trans olefin selectivity; both secondary and tertiary ether products can be obtained. The examples provided include the catalytic synthesis of an optically pure cyclopentyl epoxide and dimethyl acetal. Mechanistic studies suggest that it is the more substituted benzylidene or silylated alkylidenes that are involved in the catalytic process (vs the corresponding Mo-methylidenes). Although electron rich benzylidenes react more efficiently, the derived electron poor Mo complexes promote AROM/CM transformations as well; alkylidenes that bear a boron substituent are unreactive.

Alkenes↗
PubMed2003

Solvent-controlled diastereoselective synthesis of cyclopentane derivatives by a [3 + 2] cyclization reaction of alpha,beta-disubstituted (alkenyl)(methoxy)carbene complexes with methyl ketone lithium enolates.

Reaction of alpha,beta-unsaturated methoxycarbene complexes 1 and 11 with methyl ketone lithium enolates 2 leads to the corresponding five-membered carbocyclic compounds 4 or diast-4 and 12. The influence of the solvent and/or cosolvent (PMDTA), which turned out to be crucial to direct the reaction to 4 or diast-4, is studied, and a tentative mechanism according to these facts is proposed. In addition, the reaction of carbene complex 1a with alkynyl methyl ketone lithium enolates can be directed to the formal [3 + 2] or [4 + 1] cyclization products by a slight variation of the reaction conditions. Finally, consecutive three-component coupling reactions with carbene complex 1a, lithium enolates 2, and aldehydes 18 to give, in a diastereoselective way, hydroxy carbonyl compounds 19 and tricyclic polyethers 20 are presented.

Aldehydes↗
PubMed2000

Stereoselective synthetic approaches to highly substituted cyclopentanes via electrophilic additions to mono-, di-, and trisubstituted cyclopentenes.

Electrophilic additions to allylically substituted alkenes are of broad synthetic utility. The control of stereoselectivity in such reactions has attracted considerable interest. However, the effect of allylic and homoallylic substituents in cyclopentenyl systems has not been investigated systematically. Studies on a series of mono, di-, and trisubstituted cyclopentenes are reported in which trans-vicinal-additions favor a syn-selective approach of electrophiles to the cyclopentene system. The formal addition of HOBr, HOCl, CH(3)SCl, and dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF)/NaN(3) with a variety of cyclopentene substrates has been carried out, and the effects of various allylic substituents on these selectivities have been examined. Additions of HOBr, HOCl, and DMTSF to highly functionalized substrates proceed predictably with syn selectivity, giving predominantly or exclusively one product. Methanesulfenyl chloride additions are less predictable, but can be tuned by suitable alteration of solvent and substrate. Results have proven useful in total syntheses of (+)-trehazolin and (+)-allosamidin.

Cyclopentanes↗
PubMed2006

Stereoselective preparation of a cyclopentane-based NK1 receptor antagonist bearing an unsymmetrically substituted sec-sec ether.

A highly efficient synthesis of the potent and selective NK-1 receptor antagonist 1 is described. The key transformation involved the etherification reaction between cyclopentanol 12 and chiral imidate 30 which was catalyzed by HBF4 to initially give ether 14 as a 17:1 mixture of diastereomers and in 75% combined yield. The diastereoselectivity was upgraded to 109:1 by crystallization of the triethylamine solvate 44 which was isolated in 54% yield from 12. Mechanistic studies confirmed that the etherification reaction proceeds through an unprecedented S(N)2 reaction pathway under typical S(N)1 reaction conditions.

Cyclopentanes↗