Selective Hydroxyl Protection and Deprotection

Robertson, Jeremy; Stafford, Petra M.

doi:10.1016/b978-012312085-4/50004-0

Cited by 14 publications

(5 citation statements)

References 120 publications

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“…For example, benzyl, triphenylmethyl (trityl), and trimethylsilyl ethers, as well as 1,3-dioxolanes or 1,3-dioxanes are popular because they are quite stable over a large pH range but can be easily removed by hydrogenation, acidification, and other mild reactions. 42 …”

Section: Ethers-structure and Occurrencementioning

confidence: 97%

Chiral recognition of ethers by NMR spectroscopy

Duddeck

Gómez

2008

Chirality

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Enantiomers of chiral ethers and acetals are notoriously difficult to differentiate because their reactivity is low and they are poor donors to any Lewis acid or metal ion. As an exception, epoxides are somewhat better donors. This review describes the properties of ethers, explains NMR methods for their chiral recognition and describes successful examples of ether differentiation. The majority of literature reports deals with chiral lanthanide shift reagents and dirhodium tetracarboxylate complexes, which were used as enantiopure auxiliaries to create diastereomeric adducts with dispersed (1)H and (13)C NMR signals. The various methods are compared as to which is best suited for which purpose.

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Section: Ethers-structure and Occurrencementioning

confidence: 97%

Chiral recognition of ethers by NMR spectroscopy

Duddeck

Gómez

2008

Chirality

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“…Sugar-based acetals are common substrates in carbohydrate synthesis [15]. De Jongh and Biemann described the relationship between EI mass spectra of O-isopropylidene derivatives and their molecular weight, ring size and position, and the stereochemistry of the monosaccharide precursors, thus highlighting the importance of information obtained by such analyses in the structure elucidation and identification of monosaccharides [16].…”

Section: Reference Standards and Mass Spectrometrymentioning

confidence: 99%

Mass–Energy Profiles Obtained by Quantum Chemical Computing Applied in Mass Spectrometry: A Case Study with Identification of a Group of Acetalized Monosaccharide Isomers

et al. 2023

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Accurate modeling of small molecules substantially reduces the logistical effort and time consumption to discover and then obtain chemicals with various applications. Molecular stereochemistry is fundamentally involved in the intermolecular interactions that give rise to biological activity. Establishing the configuration of the asymmetric carbon in diastereomers can be decisive in drug design. In the presented analytical technique, on the basis of quantitative structure–fragmentation relationship (QSFR), mass–energy profiles obtained by electron ionization mass spectrometry (EI-MS) for analytes are used, along with some profiles for candidate structures calculated by quantum chemical (QC) methods. Our paper establishes the analytical conditions that lead to the best matching scores of such profiles corresponding to the actual structures for some isomers of acetalized monosaccharides. The optimization was achieved by group validation of five analytes, using four independent variables: the QC method, the descriptor of calculated energy, the impact energy of electrons, and the descriptor of experimental energy. The true structures were obtained using experimental profiles obtained at low electronic impact energies, and profiles were calculated using the DFT (B3LYP/6-31G) and RM1 QC methods. The double quantification of the ionic mass and the energy that generates it, for only a few primary ions of the mass spectrum, even allows the differentiation of acetalized diastereomers.

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“…26,27 The tin-mediated reactions of carbohydrates with acylating reagents has been an effective way to acheive differentiation between 1,2- and 1,3-diol pairs. 28 More recently, Zhang and Wong performed regioselective polyacylation reactions of various sugars using an excess of BzCl and Bu 2 SnO at higher temperatures (70–100 °C). 29 The stannylene acetal was proposed as an intermediate of the reaction of methyl α-D-glucopyranoside 1 with O-2 coordinating with the anomeric methoxy and O-6 coordinating with the ring oxygen.…”

Section: Synthesis Of Partially Substituted Building Blocks By Uniformentioning

confidence: 99%

“…Simple alkyl ethers such as methyl ethers are less preferred in complex carbohydrate synthesis because they are too stable to be removed. 28 Of the numerous alkyl protecting groups known, the most important are the benzyl (Bn) and allyl (All) groups and their derivatives. Direct regioselective benzylation of polyols is fairly rare.…”

Section: Synthesis Of Partially Substituted Building Blocks By Uniformentioning

confidence: 99%