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.

THE REACTION OF UNSATURATED CARBOHYDRATES WITH CARBON MONOXIDE AND HYDROGEN: V. ABSOLUTE STEREOCHEMISTRY OF ANHYDRODEOXYHEPTITOLS FROM 3,4,6-TRI-O-ACETYL-D-GLUCAL. STEREOCHEMISTRY OF HYDROFORMYLATION. CONFORMATIONAL ANALYSIS

1965 ◽  
Vol 43 (5) ◽  
pp. 1375-1381 ◽  
Author(s):  
Alex Rosenthal ◽  
Hans J. Koch
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Carbon Monoxide ◽  
Absolute Configuration ◽  
Sodium Iodide ◽  
Crystallographic Analysis ◽  
X Ray ◽  
Dicobalt Octacarbonyl ◽  
The Absolute ◽  
Compound Ii ◽  
Absolute Stereochemistry

3,4,6-Tri-O-acetyl-D-glucal reacted with carbon monoxide and hydrogen in the presence of dicobalt octacarbonyl to yield a mixture of two epimeric anhydrodeoxyheptitols, namely, 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-D-manno-heptitol (I) and 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-D-gluco-heptitol (II). De-O-acetylation of the mixture, followed by chromatographic separation, yielded crystalline 2,6-anhydro-3-deoxy-D-manno-heptitol (III) and 2,6-anhydro-3-deoxy-D-gluco-heptitol (IV). Reaction of the mixture of heptitols (I) and (II) with p-bromobenzenesulfonyl chloride, followed by fractional crystallization of the brosylates, gave pure 4,5,7-tri-O-acetyl-2,6-anhydro-1-O-(p-bromophenylsulfonyl)-3-deoxy-D-gluco-heptitol (VII). The absolute configuration of (VII) has been previously established by X-ray crystallographic analysis. The absolute configuration of (III) was established by correlation with that of (VII). The conversion of compound (II) into various derivatives is described.Reaction of 3,4,6-tri-O-acetyl-D-glucal with carbon monoxide and deuterium afforded 2,6-anhydro-3-deoxy-D-manno-heptitol-1,1,3-2H3 (XIII) and 2,6-anhydro-3-deoxy-D-gluco-heptitol-1,1,3-2H3 (XIV). Examination of the nuclear magnetic resonance (n.m.r.) spectra of the normal and deuterated anhydrodeoxyheptitols confirmed the structural assignments and showed that cis addition to the double bond took place to give (XIV).Comparison of the exchange reaction of sodium iodide with 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-1-O-tosyl-D-gluco-heptitol (VIII) and with 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-1-O-tosyl-D-manno-heptitol (XV) revealed that the equatorial primary tosyloxy group of (VIII) was exchanged by iodine twice as readily as the axial primary tosyloxy group of (XV).

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.

scholarly journals 2,4-Dimethyl-3,4-O-isopropylidene-L-arabinono-1,5-lactone

2007 ◽  
Vol 63 (3) ◽  
pp. o1128-o1130 ◽  
Author(s):  
Kathrine V. Booth ◽  
David J. Watkin ◽  
Sarah F. Jenkinson ◽  
George W. J. Fleet
Keyword(s):  
Absolute Configuration ◽  
Crystallographic Analysis ◽  
Starting Material ◽  
Relative Configuration ◽  
X Ray ◽  
Boat Form ◽  
The Absolute

The relative configuration at C-2 of 2,4-dimethyl-3,4-O-isopropylidene-L-arabinono lactone, C10H16O5, which exists in the boat form, was unequivocally established by X-ray crystallographic analysis. The absolute configuration was determined by the use of 2-C-methyl-D-ribonolactone as a starting material.

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 5-Amino-5-deoxy-2-C-hydroxymethyl-2,3-O-isopropylidene-L-lyxono-1,5-lactam

2007 ◽  
Vol 63 (3) ◽  
pp. o1409-o1411
Author(s):  
Michela Simone ◽  
George W. J. Fleet ◽  
Richard Bream ◽  
David J. Watkin
Keyword(s):  
Absolute Configuration ◽  
Catalytic Hydrogenation ◽  
Title Compound ◽  
Crystallographic Analysis ◽  
Starting Material ◽  
Relative Configuration ◽  
X Ray ◽  
Compound C ◽  
The Absolute

The relative configuration of the title compound, C9H14NO5, formed by catalytic hydrogenation of an azidolactone, has been established by X-ray crystallographic analysis. The absolute configuration was determined by the use of 2,3-O-isopropylidene-L-lyxono-1,4-lactone as the carbohydrate starting material.

The Absolute Structure of Latifoline

1992 ◽  
Vol 45 (2) ◽  
pp. 451 ◽  
Author(s):  
CCJ Culvenor ◽  
MF Mackay
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Crystallographic Analysis ◽  
Salt Hydrate ◽  
Space Group ◽  
X Ray ◽  
Orthorhombic Crystals ◽  
The Absolute ◽  
Absolute Structure

The absolute structure of latifoline, a pyrrolizidine diester alkaloid of retronecine and latifolic and angelic acids, has been defined by single-crystal X-ray crystallographic analysis of the hydrobromide salt hydrate. Orthorhombic crystals of C20H27NO7.HBr.H2O belong to the space group P 2′2′2′ with a 7.279(1), b 17.898(3), c 17.922(2) � and V 2334-9(8) � 3 . The structure has been refined to an R index of 0.054 for 1725 observed terms. The absolute configuration has been assigned by comparison with that of retronecine and also determined independently by X-ray examination of selected Bijvoet pairs. Our results have shown that the absolute structure of latifolic acid is 13S,14R,19S (2R,3S,4S in latifolic acid numbering), and not the stereoisomer reported recently by Roitman and Wong.

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.

scholarly journals (2S,4S)-4-Azido-1-benzyl-2-[(S)-2,2-dimethyl-1,3-dioxolan-4-yl]pyrrolidine

2006 ◽  
Vol 62 (7) ◽  
pp. o2983-o2985 ◽  
Author(s):  
Amy K. S. Chesterton ◽  
Sarah F. Jenkinson ◽  
Nigel A. Jones ◽  
George W. J. Fleet ◽  
David J. Watkin
Keyword(s):  
Absolute Configuration ◽  
Title Compound ◽  
Crystal Packing ◽  
Crystallographic Analysis ◽  
Starting Material ◽  
X Ray ◽  
Compound C ◽  
Relative Stereochemistry ◽  
The Absolute

The relative stereochemistry of the title compound, C16H22N4O2, a key intermediate in the synthesis of 3-deoxy imino sugars, was firmly established by X-ray crystallographic analysis. The absolute configuration was inferred from the starting material, D-galactose. There are no unusual crystal packing features.

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