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Journal ArticleDOI

.alpha.-Methoxy-.alpha.-trifluoromethylphenylacetic acid, a versatile reagent for the determination of enantiomeric composition of alcohols and amines

01 Sep 1969-Journal of Organic Chemistry (American Chemical Society)-Vol. 34, Iss: 9, pp 2543-2549
About: This article is published in Journal of Organic Chemistry.The article was published on 1969-09-01. It has received 2312 citations till now. The article focuses on the topics: Reagent.
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Journal ArticleDOI
TL;DR: In this paper, the application of (S)-1,10-binaphthyl-2,20-diol as NMR chiral solvating agent (CSA) for omeprazole, and three of its analogs (lanso-, panto-, and rabe-prazole) was investigated.
Abstract: The application of (S)-1,10-binaphthyl-2,20-diol as NMR chiral solvating agent (CSA) for omeprazole, and three of its analogs (lanso-, panto-, and rabe-prazole) was investigated. The formation of diastereomeric host–guest complexes in solution between the CSA and the racemic substrates produced sufficient NMR signal splitting for the determination of enantiomeric excesses by Hor F-NMR spectroscopy. Using of hydrophobic deuterated solvents was mandatory for obtaining good enantiodiscrimination, thus suggesting the importance of intermolecular hydrogen bonds in the stabilization of the complexes. The method was applied to the fast quantification of the enantiomeric purity of in-process samples of S-omeprazole. Chirality 00:000–000, 2009. VC 2009

885 citations

Journal ArticleDOI
TL;DR: This poster presents a probabilistic analysis of the response of Na6(CO3)(SO4)(SO3) to Na2SO4 using a high-resolution X-ray diffraction analysis for the stationary phase.
Abstract: Department of Chemistry, Tianjin University, Tianjin 300072, China; Department of Applied Chemistry, China Agricultural University, Beijing 100193, China; UMR 6014 CNRS, Laboratoire COBRA de l’IRCOF, Université et INSA de Rouen, Rue Tesniere, F-76130 Mont Saint Aignan, France; and Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai 200032, China

851 citations

Journal ArticleDOI
TL;DR: By analyzing the sign of the difference in chemical shifts for a number of analogous pairs of protons in the diastereomeric esters (or amides), the absolute configuration of the original carbinol (or amino) stereocenter can be reliably deduced.
Abstract: This protocol details the most commonly used nuclear magnetic resonance (NMR)-based method for deducing the configuration of otherwise unknown stereogenic, secondary carbinol (alcohol) centers (R1R2CHOH (or the analogous amines where OH is replaced by NH2)). This 'Mosher ester analysis' relies on the fact that the protons in diastereomeric alpha-methoxy-alpha-trifluoromethylphenylacetic acid (MTPA) esters (i.e., those derived from conjugation of the carbinol under interrogation with MTPA) display different arrays of chemical shifts (deltas) in their 1H NMR spectra. The protocol consists of the following: (i) preparation of each of the diastereomeric S- and R-MTPA esters and (ii) comparative (Delta delta(SR)) analysis of the 1H NMR spectral data of these two esters. By analyzing the sign of the difference in chemical shifts for a number of analogous pairs of protons (the set of Delta delta(SR) values) in the diastereomeric esters (or amides), the absolute configuration of the original carbinol (or amino) stereocenter can be reliably deduced. A typical Mosher ester analysis requires approximately 4-6 h of active effort over a 1- to 2-d period.

608 citations


Cites methods from ".alpha.-Methoxy-.alpha.-trifluorome..."

  • ...Alternatively, the acid chlorides 3S and 3R (MTPA-Cl), derived from 2R and 2S , respectively, can be used directly as active acylating agent...

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Journal ArticleDOI
TL;DR: The use of pseudoephedrine as a chiral auxiliary for asymmetric synthesis is described in full in this article, where both enantiomers of pseudo-ephedrin are inexpensive commodity chemicals and can be N-acylated in high yields to form tertiary amides.
Abstract: The use of pseudoephedrine as a practical chiral auxiliary for asymmetric synthesis is described in full. Both enantiomers of pseudoephedrine are inexpensive commodity chemicals and can be N-acylated in high yields to form tertiary amides. In the presence of lithium chloride, the enolates of the corresponding pseudoephedrine amides undergo highly diastereoselective alkylations with a wide range of alkyl halides to afford α-substituted products in high yields. These products can then be transformed in a single operation into highly enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones.

484 citations

Journal ArticleDOI
TL;DR: The many applications of selectfluor are documented and possible mechanistic pathways for its reaction are discussed and this reagent is described as one of the most reactive electrophilic fluorinating reagents available, but it is also safe, nontoxic, and easy to handle.
Abstract: The replacement of hydrogen atoms with fluorine substituents in organic substrates is of great interest in synthetic chemistry because of the strong electronegativity of fluorine and relatively small steric footprint of fluorine atoms. Many sources of nucleophilic fluorine are available for the derivatization of organic molecules under acidic, basic, and neutral conditions. However, electrophilic fluorination has historically required molecular fluorine, whose notorious toxicity and explosive tendencies limit its application in research. The necessity for an electrophilic fluorination reagent that is safe, stable, highly reactive, and amenable to industrial production as an alternative to very hazardous molecular fluorine was the inspiration for the discovery of selectfluor. This reagent is not only one of the most reactive electrophilic fluorinating reagents available, but it is also safe, nontoxic, and easy to handle. In this Review we document the many applications of selectfluor and discuss possible mechanistic pathways for its reaction.

481 citations