Enantioselective ester hydrolyses using Rhizopusnigricans: stereoselective synthesis and absolute stereochemistry of (−)-cis- and (−)-trans-1-hydroxy-4-methyl-1,2,3,4-tetrahydronaphthalene

1985 ◽  
Vol 63 (6) ◽  
pp. 1287-1291 ◽  
Author(s):  
Masaji Kasai ◽  
Herman Ziffer ◽  
J. V. Silverton
Keyword(s):  
Stereoselective Synthesis ◽  
Chiral Alcohols ◽  
Enantioselective Hydrolysis ◽  
Chemical Transformations ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cis And Trans ◽  
Hydrolysis Of ◽  
Absolute Stereochemistry

Enantioselective hydrolysis of racemic acetates of cis- and trans-1-hydroxy-4-methyl-1,2,3,4-tetrahydronaphthalene using Rhizopusnigricans yields chiral alcohols. The absolutestereochemistry of these compounds, and that of a key intermediate in their stereoselective synthesis, r-1-hydroxy-2,t-bromo-4,c-methyl-1,2,3,4-tetrahydronaphthalene, were determined by chemical transformations to 1-oxo-4-methyl-1,2,3,4-tetrahydronaphthalene of known absolute stereochemistry. The relativestereochemistry of the acetate of the key intermediate was established by X-ray crystallography.

Preparation of chiral allylic alcohols using Rhizopusnigricans. Use of the Harada–Nakanishi exciton chirality method for verifying configurational assignments of allylic alcohols

1987 ◽  
Vol 65 (3) ◽  
pp. 574-582 ◽  
Author(s):  
Satoru Ito ◽  
Masaji Kasai ◽  
Herman Ziffer ◽  
J. V. Sllverton
Keyword(s):  
Allylic Alcohols ◽  
Enantioselective Hydrolysis ◽  
Chemical Methods ◽  
Chiroptical Properties ◽  
X Ray ◽  
X Ray Crystallography ◽  
Hydrolysis Of

A series of (R) acyclic and cyclic allylic alcohols was prepared by enantioselective hydrolysis of acetates using Rhizopusnigricans. The configurations of the alcohols formed were established by chemical methods and, in the case of 1,2-benzocyclohepta-1,3-dien-5-yl camphanate, by X-ray crystallography. In conjunction with the Harada–Nakanishi rule, the chiroptical properties of the p-bromobenzoate esters were used to verify configurations tentatively assigned from their method of preparation.

Preparation and structural analysis of (±)-threo-ritalinic acid

2013 ◽  
Vol 69 (11) ◽  
pp. 1225-1228 ◽  
Author(s):  
Sara Wyss ◽  
Irmgard A. Werner ◽  
W. Bernd Schweizer ◽  
Simon M. Ametamey ◽  
Selena Milicevic Sephton
Keyword(s):  
Methyl Ester ◽  
Free Acid ◽  
Nmr Analysis ◽  
Intermolecular Hydrogen Bonds ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ph Values ◽  
Ritalinic Acid ◽  
Methyl Phenidate ◽  
Hydrolysis Of

Hydrolysis of the methyl ester (±)-threo-methyl phenidate afforded the free acid in 40% yield,viz.(±)-threo-ritalinic acid, C13H17NO2. Hydrolysis and subsequent crystallization were accomplished at pH values between 5 and 7 to yield colourless prisms which were analysed by X-ray crystallography. Crystals of (±)-threo-ritalinic acid belong to theP21/nspace group and form intermolecular hydrogen bonds. An antiperiplanar disposition of the H atoms of the (HOOC—)CH—CHpygroup (py is pyridine) was found in both the solid (diffraction analysis) and solution state (NMR analysis). It was also determined that (±)-threo-ritalinic acid conforms to the minimization of negativegauche+–gauche−interactions.

scholarly journals Mechanism of IPPase shown by high resolution Neutron and X-ray crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C1211-C1211
Author(s):  
Joseph Ng ◽  
Ronny Hughes ◽  
Michelle Morris ◽  
Leighton Coates ◽  
Matthew Blakeley ◽  
...  
Keyword(s):  
High Resolution ◽  
Active Site ◽  
Inorganic Pyrophosphatase ◽  
Inorganic Pyrophosphate ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cellular Processes ◽  
Crystallographic Structures ◽  
Hydrolysis Of ◽  
Low Energy Conformations

Soluble inorganic pyrophosphatase (IPPase) catalyzes the hydrolysis of inorganic pyrophosphate (PPi) to form orthophosphate (Pi). The action of this enzyme shifts the overall equilibrium in favor of synthesis during a number of ATP-dependent cellular processes such as in the polymerization of nucleic acids, production of coenzymes and proteins and sulfate assimilation pathways. Two Neutron crystallographic (2.10-2.50Å) and five high-resolution X-ray (0.99Å-1.92Å) structures of the archaeal IPPase from Thermococcus thioreducens have been determined under both cryo and room temperatures. The structures determined include the recombinant IPPase bound to Mg+2, Ca+2, Br-, SO2-2 or PO4-2 involving those with non-hydrolyzed and hydrolyzed pyrophosphate complexes. All the crystallographic structures provide snapshots of the active site corresponding to different stages of the hydrolysis of inorganic pyrophosphate. As a result, a structure-based model of IPPase catalysis is devised showing the enzyme's low-energy conformations, hydration states, movements and nucleophile generation within the active site.

scholarly journals Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

2021 ◽  
Vol 17 ◽  
pp. 983-990
Author(s):  
Ákos Bajtel ◽  
Mounir Raji ◽  
Matti Haukka ◽  
Ferenc Fülöp ◽  
Zsolt Szakonyi
Keyword(s):  
Alkaline Hydrolysis ◽  
Stereoselective Synthesis ◽  
2D Nmr ◽  
Ring Closure ◽  
Spectroscopic Techniques ◽  
Reductive Alkylation ◽  
X Ray ◽  
Relative Stereochemistry ◽  
Hydrolysis Of

A library of pinane-based 2-amino-1,3-diols was synthesised in a stereoselective manner. Isopinocarveol prepared from (−)-α-pinene was converted into condensed oxazolidin-2-one in two steps by carbamate formation followed by a stereoselective aminohydroxylation process. The relative stereochemistry of the pinane-fused oxazolidin-2-one was determined by 2D NMR and X-ray spectroscopic techniques. The regioisomeric spiro-oxazolidin-2-one was prepared in a similar way starting from the commercially available (1R)-(−)-myrtenol (10). The reduction or alkaline hydrolysis of the oxazolidines, followed by reductive alkylation resulted in primary and secondary 2-amino-1,3-diols, which underwent a regioselective ring closure with formaldehyde or benzaldehyde delivering pinane-condensed oxazolidines. During the preparation of 2-phenyliminooxazolidine, an interesting ring–ring tautomerism was observed in CDCl3.

scholarly journals Structure and mechanism of ATP-binding cassette transporters

2008 ◽  
Vol 364 (1514) ◽  
pp. 239-245 ◽  
Author(s):  
Kaspar P Locher
Keyword(s):  
Abc Transporters ◽  
Integral Membrane Proteins ◽  
Atp Binding ◽  
X Ray ◽  
X Ray Crystallography ◽  
Binding Domains ◽  
Mechanistic Insight ◽  
Future Challenges ◽  
Hydrolysis Of ◽  
Atp Binding Cassette

ATP-binding cassette (ABC) transporters constitute a large superfamily of integral membrane proteins that includes both importers and exporters. In recent years, several structures of complete ABC transporters have been determined by X-ray crystallography. These structures suggest a mechanism by which binding and hydrolysis of ATP by the cytoplasmic, nucleotide-binding domains control the conformation of the transmembrane domains and therefore which side of the membrane the translocation pathway is exposed to. A basic, conserved two-state mechanism can explain active transport of both ABC importers and ABC exporters, but various questions remain unresolved. In this article, I will review some of the crystal structures and the mechanistic insight gained from them. Future challenges for a better understanding of the mechanism of ABC transporters will be outlined.

scholarly journals Hydrolysis of Scandium Alkyl Derivatives Supported by a Pentadentate Diborate Ligand: Interconversion of Hydroxo and Oxo Complexes

2019 ◽  
Author(s):  
Daniel W. Beh ◽  
Warren Piers ◽  
Laurent Maron ◽  
Yan Yang ◽  
Benjamin S. Gelfand ◽  
...  
Keyword(s):  
Solid State ◽  
Hydroxo Complex ◽  
Ambient Atmosphere ◽  
X Ray ◽  
X Ray Crystallography ◽  
Hydrolysis Products ◽  
Alkyl Derivatives ◽  
Rapid Formation ◽  
Hydrolysis Of ◽  
Pentadentate Ligand

Uncontrolled reaction of water with scandium alkyls (compounds <b>1-R</b>) supported by a dianionic, pentadentate ligand leads to rapid formation of an oxo-bridged dimer (<b>2</b>). Solid state samples can be exposed to ambient atmosphere to generate samples enriched in the bridging dihydroxo dimer <b>3</b>, which slowly converts to the m-oxo species with elimination of water. DFT computations show that <b>3</b> is actually more thermodynamically stable than <b>2</b>, but the reactivity of <b>3</b> with the water eliminated leads to its decomposition to <b>2</b> and several hydrolysis products. Some of these products were characterized by X-ray crystallography, specifically a hexameric scandium dihydroxo cluster (<b>4</b>) in which the pentadentate ligand has partially demetallated. Attempts to synthesize hydroxo complex <b>3</b> by protonation of <b>2</b> also lead to hydrolysis products.

Halogenation of Tris(amido)tantalacarboranes with Dihalomethanes CH2X2 (X = Cl, Br)

2002 ◽  
Vol 67 (6) ◽  
pp. 791-807 ◽  
Author(s):  
Mark A. Fox ◽  
Andrés E. Goeta ◽  
Andrew K. Hughes ◽  
John M. Malget ◽  
Ken Wade
Keyword(s):  
Single Crystal ◽  
Prolonged Exposure ◽  
Chemical Shifts ◽  
Amide Group ◽  
The Other ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Hydrolysis Of

Slow reactions of isomeric metallacarboranes of general formulae [(NMe2)3TaC2B9H11] (3 isomers) and [(NMe2)3TaC2B9H10Me] (3 isomers) with CD2Cl2 afford quantitative yields of monochloro complexes [Cl(NMe2)2TaC2B9H11] and [Cl(NMe2)2TaC2B9H10Me]. Exposure to CD2Cl2 for months leads to solutions containing about 70% of the dichlorides in three cases. More prolonged exposure of these and the other monochlorides leads to a mixture of boron-substituted complexes. Hydrolysis of [3,3,3-(NMe2)3-3,1,2-TaC2B9H11] by moist toluene results in the formation of the oxo-bridged complex 3,3'-[3,3-(NMe2)2-3,1,2-TaC2B9H11]2(μ-O), characterised by single-crystal X-ray crystallography. The limited solubility of the latter complex in CD2Cl2 eliminates the presence of this compound in the reaction of [3,3,3-(NMe2)3-3,1,2-TaC2B9H11] with CD2Cl2. The reaction of [2,2,2-(NMe2)3-2,1,12-TaC2B9H11] with CH2Br2 in C6D6 quantitatively yields the monobromide [2-Br-2,2-(NMe2)2-2,1,12-TaC2B9H11]. Prolonged reaction with CH2Br2 leads directly to isomeric boron-substituted complexes with no evidence for dibromides. The influence on 11B, 13C and 1H NMR chemical shifts of replacing an amide group in [(NMe2)3TaC2B9H11] with chloride to give [Cl(NMe2)2TaC2B9H11] is also discussed.

Halogenated Metabolites of the Red Alga Plocamium cruciferum

1979 ◽  
Vol 32 (11) ◽  
pp. 2545 ◽  
Author(s):  
P Bates ◽  
JW Blunt ◽  
MP Hartshorn ◽  
AJ Jones ◽  
MHG Munro ◽  
...  
Keyword(s):  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Complex Mixture ◽  
Red Alga ◽  
Organic Extract ◽  
X Ray ◽  
X Ray Crystallography ◽  
Halogenated Metabolites ◽  
Acid Methyl ◽  
Absolute Stereochemistry

The organic extract of Plocamium cruciferum gave a complex mixture of fatty acid methyl esters (26%), the tribromotrichloroalkene (12),(7%), n-heptadecane (0.4%), phytol(12%) and the unusual hydroxy bisnor-monoterpene (15) (43%). The absolute stereochemistry of the polyhalogenated alkene (12) was established by X-ray crystallography.

Stereoselective Synthesis of the Two trans-(16-Hydroxymethyl)-3-methoxy-13α-estra-1,3,5(10)-trien-17-ol Isomers

2003 ◽  
Vol 68 (6) ◽  
pp. 1141-1148 ◽  
Author(s):  
Erzsébet Mernyák ◽  
János Wölfling ◽  
Gábor Bunkóczi ◽  
Lingfei Luo ◽  
Thomas R. Schneider ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Stereoselective Synthesis ◽  
X Ray ◽  
X Ray Crystallography

Reduction of 16-(hydroxymethylidene)-3-methoxy-13α-estra-1,3,5(10)-trien-17-one yielded a mixture of two diastereomeric diols in the 6:1 ratio. The configurations of the newly formed stereogenic centres were determined by X-ray crystallography and NMR spectroscopy (NOE experiments) on the compounds in their cyclic acetaldehyde acetal forms.

Synthesis, Crystal Structures, and Reactions of 2-Oxomalonylbis(arylimidoyl) Chlorides and Hydroxymethane Tris(arylimidoyl) Chlorides

2005 ◽  
Vol 58 (7) ◽  
pp. 522
Author(s):  
Richard J. Bowen ◽  
Judy Caddy ◽  
Mabel E. Coyanis ◽  
Manuel A. Fernandes ◽  
Marcus Layh ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Crystal Structures ◽  
X Ray ◽  
X Ray Crystallography ◽  
Hydrolysis Of

The 2-oxomalonylbis(arylimidoyl) chlorides [C6H3(R2-2,6)N=CCl]2CO (R = Me, 3a; Pri, 3b; H, 3c) were synthesized from C6H3(R2-2,6)NHCHO and an excess of (COCl2)3 and their reaction with various nucleophiles was studied. Successive hydrolysis of 3a led to the formation of [C6H3(Me2-2,6)N=CCl]3COH 4a and [C6H3(Me2-2,6)NHCO]3COH 5a, while treatment of 3a with HAuCl4(H2O)x gave {[C6H3(Me2-2,6)N(H)=CCl][C6H3(Me2-2,6)NHCO]2COH}AuCl4 6a. All compounds were fully characterized by microanalysis, NMR spectroscopy, mass spectrometry, and, in the case of 3a, 4a, 5a, and 6a, by X-ray crystallography.

Sign in / Sign up

Export Citation Format

Share Document