scholarly journals A Conformational Model for MTPA Esters of Chiral N-(2-Hydroxyalkyl)acrylamides

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Eduardo M. Rustoy ◽  
Alicia Baldessari ◽  
Leandro N. Monsalve
Keyword(s):  
Computational Experiments ◽  
H Nmr ◽  
Conformational Model ◽  
The Absolute ◽  
Absolute Stereochemistry

The absolute stereochemistry of novel chiral N-(2-hydroxylalkyl)acrylamides prepared by a lipase-catalyzed resolution was successfully determined by 1H NMR of their MTPA esters. The method was validated for this particular case by computational experiments.

Determination of the absolute stereochemistry of the fungal metabolite (R)-(−)-2-(4′-hydroxyphenyl)-2-hydroxyethanoic acid (pisolithin B)

1991 ◽  
Vol 69 (5) ◽  
pp. 772-778 ◽  
Author(s):  
Youla S. Tsantrizos ◽  
Kelvin K. Ogilvie
Keyword(s):  
Absolute Configuration ◽  
Lithium Aluminum Hydride ◽  
Optical Rotation ◽  
Aluminum Hydride ◽  
Lithium Aluminum ◽  
Fungal Metabolite ◽  
H Nmr ◽  
The Absolute ◽  
Absolute Stereochemistry

The antifungal antibiotic pisolithin B (p-hydroxymandelic acid, 2-(4′-hydroxyphenyl)-2-hydroxyethanoic acid, 1a) was shown to have the absolute (R) configuration. The stereochemistry was established via comparison of its optical rotation to that of its synthetic (R) and (S) enantiomers. The synthetic samples were prepared by the stereospecific reduction of the prochiral α-keto acid, p-hydroxybenzoylformic acid (2-(4′-hydroxyphenyl)-2-oxoethanoic acid, 2a), with (R) or (S)-2,2′-dihydroxy-1,1′-binaphthyl lithium aluminum hydride (BINAL-H). The absolute configuration and enantiomeric purity of both products were determined using the 1H NMR of their isobutyl esters in the presence of the chiral solvating agent (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol. Key words: pisolithin B, p-hydroxymandelic acid, antifungal, absolute configuration.

scholarly journals Determination of Absolute Stereochemistry of Natural Alicyclic Glycosides by 1H NMR Spectroscopy without Application of Chiral Reagents – An Indication

2011 ◽  
Vol 6 (5) ◽  
pp. 1934578X1100600 ◽  
Author(s):  
Tatyana N. Makarieva ◽  
Larisa K. Shubina ◽  
Alla G. Guzii ◽  
Natalya V. Ivanchina ◽  
Vladimir A. Denisenko ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Absolute Configuration ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
H Nmr ◽  
Steroid Glycosides ◽  
The Absolute ◽  
Absolute Stereochemistry

A study has been made of the 1H NMR spectra of peracetylated β-glucopyranosides and α-arabinopyranosides obtained by reaction of D- and L-glucoses, and L- and D-arabinoses with either ( R)- or ( S)-2-octanols. The obtained and literature data show that 1H NMR spectra may be used to determine the absolute configuration of the aglycone moieties of some alicyclic glycosides without the need to synthesize derivatives with chiral reagents, as long as the absolute configuration of their monosaccharide moiety is known or vice versa. Spectra of marine steroid glycosides and their acetates containing glycosylated side chains as alicyclic fragments were also examined. It was shown that analysis of 1H NMR spectra for the determination of the absolute configuration is more applicable in the cases when glycosides have the same substitution in the D-ring of the aglycone moiety.

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.

Determination of the Absolute Stereochemistry of Cyclosmenospongine

2003 ◽  
Vol 66 (9) ◽  
pp. 1263-1265 ◽  
Author(s):  
Natalia K. Utkina ◽  
Vladimir A. Denisenko ◽  
Olga V. Scholokova ◽  
Aleksandra E. Makarchenko
Keyword(s):  
The Absolute ◽  
Absolute Stereochemistry

Stereoselective deprotonation of tropinone and reactions of tropinone lithium enolate

1992 ◽  
Vol 70 (10) ◽  
pp. 2618-2626 ◽  
Author(s):  
Marek Majewski ◽  
Guo-Zhu Zheng
Keyword(s):  
Acetic Acid ◽  
Ring Opening ◽  
Aldol Reaction ◽  
Ethyl Chloroformate ◽  
Lithium Diisopropylamide ◽  
Silver Acetate ◽  
Lithium Amides ◽  
Lithium Enolate ◽  
The Absolute ◽  
Absolute Stereochemistry

Tropinone (6) was deprotonated with lithium diisopropylamide and with chiral lithium amides (18–24) and the resulting enolates (two enantiomers) were treated with electrophiles. The aldol reaction with benzaldehyde and deuteration were both diastereoselective. The former yielded only one isomer (exo, anti) of the aldol 8a; the latter proceeded from the exo face. This selectivity permitted us to probe the deprotonation of tropinone with lithium amides; it was concluded that the reaction involves predominantly the exo axial protons. The reaction of tropinone enolate with ethyl chloroformate led, via a ring opening, to the cycloheptenone derivative 9. The reaction with methyl cyanoformate yielded, in the presence of silver acetate and acetic acid, the β-ketoester 8b; however, in the absence of these additives, and especially when 12-crown-4 was added to the enolate, a ring opening leading to the pyrrolidine derivative 10 occurred instead. Deprotonation of tropinone with chiral lithium amides proceeded with modest enantioselectivity. A synthesis of non-racemic anhydroecgonine via this strategy allowed establishing the absolute stereochemistry of deprotonation.

First synthesis and determination of the absolute stereochemistry of iso-cladospolide-B and cladospolides-B and C

2006 ◽  
Vol 47 (37) ◽  
pp. 6537-6540 ◽  
Author(s):  
G.V.M. Sharma ◽  
K. Laxmi Reddy ◽  
J. Janardhan Reddy
Keyword(s):  
The Absolute ◽  
Absolute Stereochemistry

The absolute stereochemistry of the ester functions of fumonisin B1

1999 ◽  
Vol 40 (24) ◽  
pp. 4515-4518 ◽  
Author(s):  
Oliver E. Edward ◽  
Barbara A. Blackwell ◽  
Alex B. Driega ◽  
Corrine Bensimon ◽  
John W. ApSimon
Keyword(s):  
Fumonisin B1 ◽  
The Absolute ◽  
Absolute Stereochemistry

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).

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