Synthese und Absolute Konfiguration von (+)-1-Amino-2-propanthiol·HCl / Synthesis and Absolute Configuration of ( + )-1-Amino-2-propanethiol · HCl

1987 ◽  
Vol 42 (5) ◽  
pp. 617-622 ◽  
Author(s):  
Sigurd Elz ◽  
Martin Dräger ◽  
Hans-Joachim Sattler ◽  
Walter Schunack
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
X Ray ◽  
Single Diastereomer ◽  
Important Intermediate ◽  
The Absolute ◽  
C Nmr

)-4a-The structure of (-)-5-methyl-2-phenylthiazolidine (( -)-4a), an intermediate in the synthesis of (+)-1-amino-2-propanethiol · HCl ((+)-2 · HCl), was elucidated by 1H and 13C NMR spectroscopy. In contrast to earlier findings it was shown that the important intermediate ( -)-4a is not a single diastereomer but represents a 1:1 mixture of (2R,5Sand ((2S,5S)-4a-diastereomers. The absolute configuration of the (2S,3S)-di-O-(4-toluoyl)tartrate of the disulfide (5) derived from (+)-2 · HCl was determined to be (S,S) using X-ray technique.

Immobilisierung von Cytidin und Uridin über 2'.3'-O-cyclische Acetalderivate an Agarose / Im mobilisation of Cytidine and Uridine via 2',3'-O-Cyclic Acetal Derivatives to Agarose

1978 ◽  
Vol 33 (1-2) ◽  
pp. 56-60 ◽  
Author(s):  
Frank Seela ◽  
Helmut Roseineyer
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
Alkaline Hydrolysis ◽  
Carboxyl Groups ◽  
Cyclic Acetal ◽  
Ethyl Group ◽  
Ethyl Levulinate ◽  
The Absolute ◽  
Hydrolysis Of ◽  
C Nmr

Abstract Condensation of cytidine or uridine with ethyl levulinate leads to the acetals 1a/2a. The reac­tion would be expected to give mixtures of diastereoisom ers. As shown by 1H and 13C NMR spectroscopy only one diastereoisomer is formed. By spectroscopic comparison of 1a/2a with the corresponding adenosine acetal the absolute configuration of the new chiral centre was found to be R. The acetal m ethyl group of 1a/2a in exo-location can serve to distinguish the two m ethyl signals of O-2′,3′-isopropylidenecytidine and -uridine in the NM R spectra. On alkaline hydrolysis of the esters the acids 1b and 2b are formed, which can be condensed through their carboxyl groups with 6-aminohexylagarose. The affinity resins 3 and 4 contain 7.1 μmol and 7.6 μmol ligand/g moist gel respectively. A biospecificity of the new polymers to cytidine-and uridine converting enzymes is expected.

Enantioselective Diels-Alder reaction of (E)-1-trimethylsilyloxy-1,3-butadiene with chiral glyoxylates

1990 ◽  
Vol 55 (1) ◽  
pp. 230-244 ◽  
Author(s):  
Otakar Červinka ◽  
Aleš Svatoš ◽  
Petr Trška ◽  
Pavel Pech
Keyword(s):  
Nmr Spectroscopy ◽  
Quantum Chemical Calculations ◽  
Absolute Configuration ◽  
Quantum Chemical ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Chemical Correlation ◽  
The Absolute ◽  
C Nmr

Enantioselective Diels-Alder reaction of (E)-1-trimethylsilyloxy-1,3-butadiene (I) with chiral (-)-menthyl (II) and (-)-8-phenylmenthyl (III) glyoxylates in various solvents without or with catalysts was studied. The reactions gave a mixture of trans-and cis-isomers of (-)-menthyl (IV) and (-)-8-phenylmenthyl (V) 2-trimethylsilyloxy-5,6-dihydro-2H-pyran-6-carboxylates. The regioselectivity of the reaction was explained by quantum-chemical calculations, the enantioselectivity was determined using 13C NMR spectroscopy and the absolute configuration of the addition products was assigned on the basis of chemical correlation with (S)-(-)-dimethyl malate.

Structures and Synthesis of 4a-Homo-7,19-dinorsteroids, X-Ray Crystallography and NMR Spectroscopy

1999 ◽  
Vol 64 (12) ◽  
pp. 2019-2034 ◽  
Author(s):  
Alexander Kasal ◽  
Miloš Buděšínský ◽  
Jan Pelnař ◽  
Michael A. Bruck ◽  
Michael F. Brown
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
Starting Material ◽  
Nmr Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Leaving Group ◽  
The Absolute ◽  
Related Compounds

X-Ray diffraction revealed the absolute configuration of 4aβ-methyl-4a-homo-7,19-dinor- 5α,10α-androstane-3,17-dione. Detailed NMR analysis suggested that the 5α configuration existed in the starting material, 3β-acetoxy-4a-methylidene-4a-homo-7,19-dinor- 5α-androst-9-en-17-one, and related compounds. Thus 5-methyl-5β-estr-9-ene derivatives with a leaving group in position 6β were found to react with nucleophiles to form rearranged 4a-homo-7,19-dinorandrostane derivatives with a 5α configuration.

scholarly journals Punctaporonins N–S, New Caryophyllene Sesquiterpenoids from Cytospora sp.

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Yan Li ◽  
Qingbin Wang ◽  
Xingzhong Liu ◽  
Yongsheng Che
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
Hela Cells ◽  
Crystallographic Analysis ◽  
X Ray ◽  
The Absolute

Six new caryophyllene sesquiterpenoids, punctaporonins N–S (1–6), and three known ones, 6-hydroxypunctaporonins B (7), A (8), and E (9), have been isolated from solid cultures of Cytospora sp. The structures of 1–6 were elucidated primarily by NMR spectroscopy. The absolute configuration of 1 was assigned by X-ray crystallographic analysis of its S-MTPA ester. Compounds 2, 5, and 6 showed modest cytotoxicity against HeLa cells.

DETERMINATION OF THE ABSOLUTE CONFIGURATION OF NEW PIPERIDIN-4-ONE DERIVATIVE FROM Pellacalyx saccardianus BY NOESY SPECTROSCOPY

2016 ◽  
Vol 78 (3-2) ◽  
Author(s):  
Salam Ahmed Abed ◽  
Hasnah Mohd Sirat
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Absolute Configuration ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Absolute ◽  
Nuclear Overhauser ◽  
Nuclear Magnetic

A new alkaloid, pellacalyxin was isolated from the leaves of Pellacalyx saccardianus of Rhizophoraceae family. Pellacalyxin was analyzed using nuclear Overhauser spectroscopy (NOESY) nuclear magnetic resonance (NMR) technique to determine the absolute configuration. The analysis of absolute configuration of pellacalyxin was supported by X-ray crystallography. 1H-1H NOESY NMR spectroscopy exhibited that pellacalyxin possesses two chiral centers (3S) and (6R).

Transition Metal Allyls, V. The Preparation and Structure of [NiX(PmenthylR1R2)(η3-allyl)] Complexes

1984 ◽  
Vol 39 (8) ◽  
pp. 1139-1150 ◽  
Author(s):  
H. Brandes ◽  
R. Goddard ◽  
P. W. Jolly ◽  
C. Krüger ◽  
R. Mynott ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Transition Metal ◽  
Absolute Configuration ◽  
Phosphorus Atom ◽  
Optically Active ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Absolute ◽  
Active Centres

A number of adducts formed by reacting [NiX(η3-allyl)]2 complexes with optically active tert.- phosphines, in which optically active centres are found both at the phosphorus atom and in a substituent, have been isolated and their structures investigated in solution by NMR spectroscopy. The absolute configuration of the phosphine in [NiCl{Pm enthyl(Me)But}(η3-C3H5)] has been determ ined by X-ray crystallography. The relevance of the results to the nickel-catalyzed asymmetric codimerisation of alkenes is discussed.

An unusual reaction of a bridged triterpenoid α-diketone with acetic anhydride

1991 ◽  
Vol 56 (12) ◽  
pp. 2917-2935 ◽  
Author(s):  
Eva Klinotová ◽  
Václav Křeček ◽  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Jaroslav Podlaha ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Acetic Anhydride ◽  
Spectral Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mild Conditions ◽  
Condensation Products ◽  
Unsaturated Lactones ◽  
C Nmr

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.

Reactivity of Sodium Hexaethyl-2,4-dicarba-nido-hexaborate(1-)

1999 ◽  
Vol 64 (6) ◽  
pp. 977-985 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hans-Jörg Schanz ◽  
Wolfgang Milius ◽  
Catherine McCammon
Keyword(s):  
Mössbauer Spectroscopy ◽  
Nmr Spectroscopy ◽  
Structural Analysis ◽  
Hydrogen Atom ◽  
Mossbauer Spectroscopy ◽  
Sandwich Complex ◽  
X Ray ◽  
Bromo Derivative ◽  
Boron Tribromide ◽  
C Nmr

Sodium hexaethyl-2,4-dicarba-nido-hexaborate(1-) (6), available from hexaethyl-2,4-dicarba- nido-hexaborane(8) (4) by deprotonation, reacts with deuterated methanol, CD3OD, to give back 4 without H/D exchange of the B-H-B hydrogen atom. The reaction of 6 with diethylboron chloride, Et2BCl, affords hexaethyl-2,4-dicarba-closo-hexaborane(6) (7), the first example of a peralkylated carborane of this type. In contrast, the reaction of 6 with boron tribromide, BBr3, leads mainly to 2,3,4,5,6,7-hexaethyl-2,4-dicarba-closo-heptaborane(7) (8), together with the corresponding 1-bromo derivative (9) and the closo-carborane 7 as side products. The reaction of two equivalents of 6 with FeCl2 gives the air-stable sandwich complex bis[hexaethyl-2,4-dicarba-nido-hexaborate(1-)]iron 10 which was characterised by X-ray structural analysis. All products were characterised by 1H, 11B and 13C NMR spectroscopy, and 57Fe Mössbauer spectroscopy was used to study 10.

Absolute Stereochemistry of (-)-Wieland-Miescher Ketone as Established by the X-ray Crystallographic and CD Exciton Chirality Methods

1992 ◽  
Vol 57 (7) ◽  
pp. 1459-1465 ◽  
Author(s):  
Nobuyuki Harada ◽  
Tatsuo Sugioka ◽  
Hisashi Uda ◽  
Takeo Kuriki
Keyword(s):  
Structure Analysis ◽  
Absolute Configuration ◽  
X Ray ◽  
The Absolute ◽  
Absolute Stereochemistry

The 8aR absolute stereochemistry of Wieland-Miescher ketone (-)-I was established by the X-ray structure analysis of its bis(4-bromobenzoate) derivatives (1R,6R,8aR)-(+)-IV and (1R,6S,8aR)-(-)-V. The absolute configuration of (-)-I was corroborated further by the application of the CD exciton chirality method to bis(4-bromobenzoates) (+)-IV and (-)-V.

scholarly journals Preparative-scale HPLC Resolution of Metallacyclic η3-Allyltricarbonyliron Complexes and Determination of the Absolute Configuration by X-Ray Crystal Structure Analysis

1999 ◽  
Vol 23 (9) ◽  
pp. 578-579
Author(s):  
Rainer Schobert ◽  
Hermann Pfab ◽  
Jutta Böhmer ◽  
Frank Hampel ◽  
Andreas Werner
Keyword(s):  
Crystal Structure ◽  
Silica Gel ◽  
Structure Analysis ◽  
Absolute Configuration ◽  
Crystal Structure Analysis ◽  
Preparative Scale ◽  
X Ray ◽  
The Absolute

Racemates of (η3-allyl)tricarbonyliron lactone complex Fe(CO)3{η1:η3-C(O)XCH2CHCMeCH2} 1a (X = O) and (η3-allyl)tricarbonyliron lactam complex 2a (X = NMe) are resolved on a preparative scale by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate/silica gel RP-8 and the absolute configuration of (-)-2a is determined by X-ray crystal structure analysis.

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