Sugar-Annulated Oxazoline Ligands: A Novel Pd(II) Complex and Its Application in Allylic Substitution

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Recent Advances in Enantioselective Pd-Catalyzed Allylic Substitution: From Design to Applications

This Review compiles the evolution, mechanistic understanding, and more recent advances in enantioselective Pd-catalyzed allylic substitution and decarboxylative and oxidative allylic substitutions. For each reaction, the catalytic data, as well as examples of their application to the synthesis of more complex molecules, are collected. Sections in which we discuss key mechanistic aspects for high selectivity and a comparison with other metals (with advantages and disadvantages) are also included. For Pd-catalyzed asymmetric allylic substitution, the catalytic data are grouped according to the type of nucleophile employed. Because of the prominent position of the use of stabilized carbon nucleophiles and heteronucleophiles, many chiral ligands have been developed. To better compare the results, they are presented grouped by ligand types. Pd-catalyzed asymmetric decarboxylative reactions are mainly promoted by PHOX or Trost ligands, which justifies organizing this section in chronological order. For asymmetric oxidative allylic substitution the results are grouped according to the type of nucleophile used.

Multifunctional chiral aminophosphines for enantiodivergent catalysis in a palladium-catalyzed allylic alkylation reaction

Trifunctional MAP-based chiral phosphines were tested as new ligands in a Pd-catalyzed asymmetric allylic alkylation, demonstrating fast and enantiodivergent catalysis. The palladium complexes of representative ligands by X-ray analysis revealed a novel mode of P,N-coordination of the ligand to the palladium center, which may contribute to switching the sense of the asymmetric induction via combined steric and tunable H-bonding interactions between the metal complex and the substrates.

Carbohydrate-Based Chiral Iodoarene Catalysts: A Survey through the Development of an Improved Catalyst Design

Iodoarene catalysts can be applied in versatile reactions, for instance in the construction of complex chiral molecules via dearomatization of simple aromatic compounds. Recently, we reported the synthesis of the first carbohydrate-based chiral iodoarene catalysts and their application in asymmetric catalysis. Here we describe the synthesis of some new and improved catalysts. An account on how we got to the improved catalyst design, as well as the X-ray structure of one of the carbohydrate-based iodoarenes, is given.

Metal complexes of 4,6-O-ethylidene-β-d-glucopyranosylamine derivatives and their application in organic synthesis

Glycosylamine derivatives of 4,6-O-ethylidene-d-glucose have been used for complexing the alkali, alkaline earth and transition metal ions. Three different series of ligands have been reported where N-(o-carboxyphenyl)-4,6-O-ethylidene-β-d-glucopyranosylamine has been used for complexing the diamagnetic (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Zn²⁺, Cd²⁺, Hg²⁺) metal ions. N-(2-Hydroxybenzoyl)-L-alanyl-4,6-O-ethylidene-β-d-glucopyranosylamine selectively interacts with molecular cupric acetate and the adduct acts as a catalyst in selective oxidation of primary and secondary alcohols into their corresponding carbonyl compounds. Salicylidene derivatives of 4,6-O-ethylidene-β-d-glucopyranosylamine have been used in complexing Ni²⁺, Cu²⁺, Zn²⁺, VO²⁺, MoO₂²⁺ and UO₂²⁺ metal ions, where Cu(II) and Mo(VI) complexes have been further used in the organic synthesis. Dinuclear copper complex exhibited catecholase like activity and also catalyzed the oxidation of primary and secondary alcohols selectively into their corresponding carbonyl compounds. Trinuclear copper complex has been reported to activate the C-Cl bond of solvent chloroform in the presence of mild organic bases below room temperature. Mo(VI) complex has been used as a catalyst for epoxidation, organic sulfide oxidation and synthesis of bis(indolyl)methanes.

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

Phosphinooxazoline (PHOX) ligands are an important class of ligands in asymmetric catalysis. We synthesized ten novel D-fructose-derived spiro-fused PHOX ligands with different steric and electronic demand. The application of two of them was tested in asymmetric allylic alkylation. The ligands are prepared in two steps from readily available 1,2-O-isopropylidene protected β-D-fructopyranoses by the BF₃·OEt₂-promoted Ritter reaction with 2-bromobenzonitrile to construct the oxazoline moiety followed by Ullmann coupling of the resulting aryl bromides with diphenylphosphine. Both steps proceeded mostly in good to high yields (57–86% for the Ritter reaction and 35–89% for the Ullmann coupling). The Ritter reaction gave two anomers, which could be separated by column chromatography. The prepared ligands showed promising results (er of up to 84:16) in Tsuji–Trost reactions with diphenylallyl acetate as model substrate.

Special Issue: Asymmetric Synthesis 2017

The use of asymmetric synthetic methodologies plays a crucial role, nowadays, in the preparation of bioactive or other interesting compounds [...].