Search results for "Stereom"
showing 10 items of 165 documents
Individual stereoisomers of phosphinic dipeptide inhibitor of leucine aminopeptidase
2008
Abstract Individual stereoisomers of the phosphinic pseudodipeptide hPheψ[P(O)(OH)CH2]Phe were obtained by stereoselective liquid chromatographic separation as N- and C-terminally protected derivative on quinidine carbamate modified silica stationary phase. The stereoisomeric purity, exceeding 95% for each fraction, was determined before and after deprotection using two independent methods. The absolute configuration was rationally assigned by application of enantiomerically pure phosphinic acid substrates in the synthetic procedure and correlation with biological activity of the products. Substantial differences in inhibition of leucine aminopeptidase by the individual isomers revealed nov…
Tucumanin, a β-hydroxy-γ-lactone bistetrahydrofuranic acetogenin from Annona cherimolia, is a potent inhibitor of mitochondrial complex I
2004
A new β-hydroxy-γ-methyl-γ-lactone bistetrahydrofuranic acetogenin, tucumanin, with the infrequent symmetrical threo/trans/threo/trans/ threo relative configuration at the tetrahydrofuran rings was isolated from Annona cherimolia (Annonaceae) seeds. The inhibitory potency on the mitochondrial complex I of acetogenins with this relative configuration (tucumanin and asimicin) was compared with that shown by the corresponding pairs with an asymmetrical threo/trans/threo/trans/erythro relative configuration (laherradurin/rolliniastatin-2, and itrabin/molvizarin). All these compounds act as selective inhibitors of mitochondrial complex 1 in the 0.18 - 1.55 nM range. Fil: Barrachina, Isabel. Univ…
(4R)-4-Hydroxy-1-[(2S)-2-hydroxydodecyl]-L-proline monohydrate
2006
The title compound, C17H33NO4·H2O, was found to be the S diastereoisomer with respect to the asymmetric C atom at the OH group on the chain. The X-ray structure was determined as part of a study of the molecular geometry and stereochemistry of l-proline derivatives for pre-coating thin-layer chromatography plates intended for enantiomeric separation.
Synthesis of all 7αH-guaia-4,11-dien-3-one diastereomers from (+)-dihydrocarvone
2005
Abstract All four 7α H -guaia-4,11-dien-3-one diastereomers have been synthesized from the common intermediate 1α H ,10α-acetoxy-7α H -guaia-4,11-dien-3-one obtained from (+)-dihydrocarvone. The spectral features of the four diasteromers have been correlated and the structure and absolute configuration of 1β H ,10β H ,7α H -guaia-4,11-dien-3-one isolated from Pleocarphus revolutus has been confirmed.
Coordination properties of imino(2-pyridyl)methylpalladium(II) compounds. Reactions with the chloride-bridged allyl dimers [MCl(η3-2-MeC3H4)]2 (MPd,…
1990
Abstract The imino(2-pyridyl)methylpalladium(II) compounds py-2-CR 1 NR [R 1 = trans -PdCl(PPh 3 ) 2 , R = C 6 H 4 OMe- p ( Ia ), Me ( Ib ), CMe 3 ( Ic ); R 1 = Pd(dmtc)(PPh 3 ), R = C 6 H 4 OMe- p ( Id )] react with [MCl(η 3 - 2-MeC 3 H 4 )] 2 (M = Pd, Pt) in a molar ratio 1/0.5 and in the presence of NaClO 4 to yield the binuclear cationic complexes II , [M(η 3 -2-MeC 3 H 4 )(py-2-CR 1 NR)]ClO 4 , where the α-diimino group acts as σ,σ N , N ′ chelating ligand. In the absence of NaClO 4 and with a molar ratio 1/1, the reaction leads initially to formation of a ionic intermediate A , [M(η 3 - 2-MeC 3 H 4 )(py-2-CR 1 NR)] [MCl 2 (η 3 -2-MeC 3 H 4 )], which subsequently undergoes exchange …
Diastereoselective synthesis of enantiomeric tertiary alcohols via nucleophilic additions to protected D- and L-erythrulose derivatives
1992
Abstract The diastereoselectivity of the addition of several organometallic reagents to the carbonyl group of protected D - and L -erythrulose derivatives has been investigated. Tertiary alcohols are stereoselectively formed, the diastereomeric ratio being markedly dependent on the reagent type, solvent and temperature.
Peptide Metal–Organic Frameworks for Enantioselective Separation of Chiral Drugs
2017
We report the ability of a chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid phase extraction (SPE) of a racemic mixture by using Cu(GHG) as extractive phase permits isolating more than 50% of the (+)-ephedrine enantiomer as target compound in only four minutes. To the best of our knowledge, this represents the first example of a MOF capable of separating ch…
Allylpalladium( II ) Complexes with Aminophosphane Ligands: Solution Behaviour and X‐ray Structure of cis ‐[Pd(η 3 ‐CH 2 CHCHPh){Ph 2 PCH 2 CHPhNH(2,…
2004
A new β-aminophosphane L2 [Ph2PCH2CH(Ph)NH(2,6-C6H3iPr2)], bearing an asymmetric carbon atom and a vicinal prochiral nitrogen centre and (η3-allyl)palladium complexes of general formula [Pd(η3-C3H4R){η2-Ph2PCH2CH(Ph)NHAr}][PF6] (1−6) (R = H, Me or Ph and Ar = Ph or 2,6-C6H3iPr2) have been synthesised. NMR spectroscopic studies and a crystal structure analysis of complex 6 (R = Ph, Ar = 2,6-C6H3iPr2) confirmed the highly diastereoselective coordination of the nitrogen atom. Because of the allyl fluxionality and the presence of asymmetric centres, all the complexes exist in solution as mixtures of up to four diastereomers. For the monosubstituted allyl complexes [Pd(η3-C3H4R){Ph2PCH2CH(Ph)NHA…
Synthesis of oligodeoxynucleotides containing diastereomeric dihydrodiol epoxide-N6-deoxyadenosine adducts of polycyclic aromatic hydrocarbons
1993
Abstract A generally applicable route is reported for the synthesis of oligodeoxynucleotides which contain structurally defined N 6 -deoxyadenosine adducts, derived from sterically highly hindered dihydrodiol epoxides of polycyclic aromatic hydrocarbons (PAH).
Stereocontrolled synthesis of five diastereomers of trimethyl 3-aminocyclopentane-1,2,4-tricarboxylates
2013
Abstract The sterically controlled oxidative cleavage of N - protected di exo - and di endo -substituted norbornene β-amino acids/esters resulted in four trimethyl 3-aminocyclopentane-1,2,4-carboxylate diastereomers. The sodium methoxide mediated isomerization of the four diastereomers in all cases yielded the thermodynamically most stable all- trans stereoisomer as a single product.