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At least 271 records · Page 15Linked to original sources
PubMed2006

General strategy for stereoselective synthesis of 1-substituted exo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octanes: total synthesis of (+/-)-gmelinol.

[reaction: see text] A general strategy for stereoselective synthesis of 1-substituted exo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octanes including (+/-)-gmelinol from (2,3-trans)-(4,5-cis)-alpha-aroylparaconic esters, which are readily obtained from the reaction of vicinal dianions derived from alpha-aroylsuccinic esters with aromatic aldehydes, is described. The synthetic sequence involves alpha-methylation or alpha-hydroxylation, reduction, bislactonization, and reduction followed by furofuran formation.

Bridged Bicyclo Compounds↗
PubMed2006

Alpha,gamma-diamino acids: asymmetric synthesis of new constrained 6-amino-3-azabicyclo[3.2.1]octane-6-carboxylic acids.

The synthesis of two new diastereomeric 6-amino-3-azabicyclo[3.2.1]octane-6-carboxylic acids exo- and endo-8,9 is reported using exo- and endo-norbornene amino acids as chiral building blocks. This method provides a fast access to optically pure amino acids 8 and 9 which can be considered both alpha,gamma- and alpha,delta-diamino acids containing sterical constraints and characterized by alpha,alpha-disubstitution.

Amino Acids, Diamino↗
PubMed1996

A Facile, Expeditious Route to the Benzooxabicyclo[3.2.1]octane System. Application to a Short, High-Yield Synthesis of Filiformin.

A facile and efficacious route to the benzooxabicyclo[3.2.1]octane system has been developed and applied to a synthesis of filiformin (1). The cycloaddition of ethylene to the methoxychromone 13 furnished the oxetanol 14 through a tandem cycloaddition and gamma-hydrogen abstraction sequence. Lithium aluminum hydride reduction to the diol 15 followed by acid-catalyzed rearrangement produced benzooxabicyclooctanone (16), arising from exclusive external bond migration. Similarly, ethoxychromone (17) under the same sequence of reactions afforded the homologous bridged ketone 20. For the synthesis of filiformin (1), methoxychromone 24 on ethylene cycloaddition followed by reduction of resultant oxetanol 25 with lithium aluminum hydride furnished diol 10. Acid-catalyzed rearrangement of 10 provided the bridged ketone 11 which was brominated to give 26. This bromo ketone had previously been converted to filiformin (1), and also aplysin 9, and hence, the present work represents a short, high-yield formal synthesis of these sequiterpenes from a single starting material.

Journal Article↗
PubMed1996

3-Hydroxy-4-pyrones as Precursors of 4-Methoxy-3-oxidopyridinium Ylides. An Expeditious Entry to Highly Substituted 8-Azabicyclo[3.2.1]octanes.

3-Hydroxy-4-pyridones, which are easily prepared from commercially available 3-hydroxy-4-pyrones, can be readily transformed into 4-methoxy-3-oxidopyridinium ylides by treatment with methyl trifluoromethanesulfonate and subsequent deprotonation with a non-nucleophilic base. These ylides are capable of undergoing cycloaddition to several electron-deficient alkenes, thus allowing the synthesis of highly functionalized azabicyclo[3.2.1]octane moieties. The rich substitution patterns of these frameworks might allow their divergent conversion to a variety of natural and non-natural tropane alkaloids.

Journal Article↗
PubMed2000

Conversion of the iridoid glucoside antirrhinoside into 3-azabicyclo[3.3.0]octane building blocks.

The iridoid glucoside antirrhinoside (1) was transformed into polysubstituted 3-azabicyclo[3.3.0]octanes 3, 12, and 13 in 4 to 5 steps. Ozonolysis of the diacetonide of 1 and of its 7-deoxy-derivative 8 afforded cyclopentanoids 2 and 10, respectively. Conditions for the selective conversion of 2 and 10 into the corresponding ditosylates 4 and 11 were investigated. Cyclization of 4 and 11 was achieved with benzylamine and 2-methoxybenzylamine to yield bicyclic pyrrolidines 3, 12, and 13. Additional building blocks 14 and 15 were obtained by selective deprotection of the N-benzyl and isopropylidene moieties in 12 and 13, respectively.

Aza Compounds↗
PubMed2001

3,8-Diazabicyclo[3.2.1]octan-2-one peptide mimetics: synthesis of a conformationally restricted inhibitor of farnesyltransferase.

A new synthesis of the 3,8-diazabicyclo[3.2.1]octan-2-one framework is described. Transannular enolate alkylation of piperazinone derivatives provides a flexible route to highly constrained bicyclic peptidomimetic synthons with substitution at the Calpha position. The chemistry was used to produce a conformationally constrained farnesyltransferase inhibitor, which aided the elucidation of enzyme-bound conformation.

Alkyl and Aryl Transferases↗
PubMed2002

Radical cascade reaction with 1,4-dienes and 1,4-enynes using 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor: one-step synthesis of bicyclo[3.3.0]octane derivatives.

[reaction: see text] Radical cascade reaction with various 1,4-dienes and 1,4-enynes using dimethyl 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor smoothly proceeds through an iodine atom transfer mechanism to give functionalized bicyclo[3.3.0]octane derivatives in good yields.

Journal Article↗
PubMed2003

Nonvolatile Me(3)P-like P-donor ligand: synthesis and properties of 4-phenyl-1-phospha-4-silabicyclo[2.2.2]octane.

[reaction: see text] A new trialkylphosphine ligand with Me(3)P-like steric and electronic properties, 4-phenyl-1-phospha-4-silabicyclo[2.2.2]octane (Ph-SMAP), was synthesized. Given a phenyl group at the silicon atom, the Ph-SMAP ligand displayed nonvolatility with retention of Me(3)P-like properties. The new ligand was air-stable, crystalline, and easy to handle.

Journal Article↗
PubMed2005

Elysiapyrones from Elysia diomedea. Do such metabolites evidence an enzymatically assisted electrocyclization cascade for the biosynthesis of their bicyclo[4.2.0]octane core?

[structure: see text] Biogenetically interesting polypropionate-derived metabolites 1 and 2, featuring an unprecedented skeleton, have been isolated from the sea slug Elysia diomedea. Their enantiomeric character indicates that the current spontaneous electrocyclization cascade biogenetic hypothesis for the bicyclo[4.2.0]octane core must be enzymatically aided. These compounds are isomeric with the 15-nor-9,10-deoxytridachione/15-norphotodeoxytridachione pair of metabolites and encourage speculation about their biosynthetic relationship.

Animals↗
PubMed2004

Construction of a C(30-38) dioxabicyclo[3.2.1]octane subtarget for (+)-sorangicin A, exploiting a regio- and stereocontrolled acid-catalyzed epoxide ring opening.

[reaction: see text] In this paper, we report assembly of the novel dioxabicyclo[3.2.1]octane subtarget (-)-2, comprising the signature structural element of the potent antibiotic (+)-sorangicin A (1). The synthesis was achieved in 15 steps (1.5% overall yield) via a series of acid-catalyzed epoxide ring openings. The first, facilitated by the complex of alkyne (+)-3 with Co(2)(CO)(8), proceeded in a highly regio- and stereoselective fashion.

Acids↗
PubMed1992

Synthesis of 2-(3-substituted-1,2,4-oxadiazol-5-yl)-8-methyl-8-azabicyclo [3.2.1]octanes and 2 alpha-(3-substituted-1,2,4-oxadiazol-5-yl)-8-methyl-8- azabicyclo[3.2.1]oct-2-enes as potential muscarinic agonists.

Radioligand binding affinities of seven muscarinic receptor ligands which possess an oxadiazole ring side chain have been determined in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations to determine the selectivity for subtypes of muscarinic receptor. The ratios of binding constants in brain membranes were measured as an indicator of potential agonist activity against [3H]QNB and [3H]Oxo-M. These muscarinic ligands did not discriminate the subtypes of muscarinic receptors. Six muscarinic ligands which have a 3-amino- or 3-methyl-1,2,4-oxadiazol-5-yl groups attached to the 8-methyl-8-azabicyclo[3.2.1]oct-2-ene or 8-methyl-8-azabicyclo[3.2.1]octane head group show binding constants between 2.04 x 10(-6) and 1.79 x 10(-5) M in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations. 1-Methyl-2-[3-amino-1,2,4-oxadiazol-5-yl]piperidine shows low binding constants of approximately 10(-4) M in rat heart and rat brain. (1R,5S)-2-[3-Amino-1,2,4-oxadiazol-5-yl]-8-methyl-8-azabicyclo- [3.2.1]oct-2-ene [(1R,5S)-17] was the most active compound.

Animals↗
PubMedDate not supplied

[Hydrophobic formate dehydrogenase from Pseudomonas sp. 101 in the system of reverse micelles of aerosol OT in octane].

NAD(+)-dependent formate dehydrogenase (FDH) was hydrophobized with palmitoyl chloride to give the samples with various modification degrees (2-10). The native and modified FDHs were comparatively studied in the system of reverse micelles of Aerosol OT in octane. Like the native, the modified enzyme displayed three maxima in the curve of dependence of its catalytic activity on the degree of surfactant hydration (the micelle size), which reflect the enzyme functioning in the form of a monomer, dimer, or octamer. The peak corresponding to the functioning of the FDH dimer was found to decrease along with an increase in the modification degree. Thus, the modified enzyme mainly functions in the form of monomer and octamer. The modified FDH displayed membranotropy and revealed the dependence of catalytic activity on surfactant concentration.

Catalysis↗
PubMed1989

Effects of S-adenosyl-1,8-diamino-3-thio-octane and S-methyl-5'-methylthioadenosine on polyamine synthesis in Ehrlich ascites-tumour cells.

The rate-limiting enzymes in polyamine biosynthesis, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), are negatively regulated by the polyamines spermidine and spermine. In the present work the spermidine synthase inhibitor S-adenosyl-1,8-diamino-3-thio-octane (AdoDATO) and the spermine synthase inhibitor S-methyl-5'-methylthioadenosine (MMTA) were used to evaluate the regulatory role of the individual polyamines. Treatment of Ehrlich ascites-tumour cells with AdoDATO caused a marked decrease in spermidine content together with an accumulation of putrescine and spermine. Treatment with MMTA, on the other hand, gave rise to a marked decrease in spermine, with a simultaneous accumulation of spermidine. A dramatic increase in the activity of AdoMetDC, but not of ODC, was observed in MMTA-treated cells. This increase appears to be unrelated to the decrease in spermine content, because a similar rise in AdoMetDC activity was obtained when AdoDATO was given in addition to MMTA, in which case the spermine content remained largely unchanged. Instead, we show that the increase in AdoMetDC activity is mainly due to stabilization of the enzyme, probably by binding of MMTA. Treatment with AdoDATO had no effects on the activities of ODC and AdoMetDC, even though it caused a precipitous decrease in spermidine content. The expected decrease in spermidine-mediated suppression of ODC and AdoMetDC was most probably counteracted by the simultaneous increase in spermine. The combination of AdoDATO and MMTA caused a transient rise in ODC activity. Concomitant with this rise, the putrescine and spermidine contents increased, whereas that of spermine remained virtually unchanged. The increase in ODC activity was due to increased synthesis of the enzyme. There were no major effects on the amount of AdoMetDC mRNA by treatment with the inhibitors, alone or in combination. However, the synthesis of AdoMetDC was slightly stimulated in cells treated with MMTA or AdoDATO plus MMTA. The present study demonstrates that regulation of neither ODC nor AdoMetDC is a direct function of the polyamine structure. Instead, it appears that the biosynthesis of the polyamines is feedback-regulated by the various polyamines at many different levels.

Adenosine↗
PubMed2004

The role of symmetry and optical selection rules in revealing the molecular structure of the lowest Rydberg and ionic states of the 1,4-diazabicyclo[2.2.2]octane-Arn (n = 1,2,3) van der Waals complexes.

The 1,4-diazabicyclo[2.2.2]octane-Arn (n = 1,2,3) van der Waals complexes (DABCO-Arn) have been investigated using a combination of (1 + 1') resonance enhanced multiphoton ionization (REMPI) and zero electron kinetic energy (ZEKE) spectroscopy. The additivity of the spectral shifts observed in both REMPI and ZEKE spectra, taken together with analysis of vibrational structure, suggest that in both DABCO-Ar and DABCO-Ar2 the argon atoms bind in equivalent equatorial (face) locations between two adjacent (CH2)2 bridges. However, the cumulative evidence from both REMPI and ZEKE spectra, together with ab initio results, suggests that the DABCO-Ar3 complex does not revert to D3h symmetry, but rather adopts a C2v structure in which all three argon atoms bind to one side of the DABCO framework. The exceptionally low wave-number vibrational structure observed in the REMPI spectra suggest that the van der Waals interaction in the excited state is extremely weak. However, ionization necessarily increases the strength of the interaction by virtue of the introduction of charge-induced dipole forces, as revealed by a consistent increase in vibrational wave numbers of the modes observed in the resultant ZEKE spectra.

Journal Article↗