Pd(II)/PhI(OAc)2 promoted direct cross coupling of glucals with aromatic acids

Advancing carbohydrate functionality: The role of hypervalent iodine

Hypervalent iodine reagents have undergone significant development and widespread application in the functionalization of carbohydrates. This is primarily attributed to their exceptional properties, including mildness, ease of handling, high selectivity, environmental friendliness, and stability. This review aims to emphasize the utilization of hypervalent iodine compounds in the functionalization of carbohydrates. The present article covers various aspects, including glycal functionalization, C-H or N-H insertion reactions, O-arylations, C-2 deoxy-2-iodo glycoconjugates, iminosugars, and C3-oxo-glycals, achieved through the use of hypervalent iodine reagents/catalysts. Additionally, it explores hypervalent iodine-mediated bioactive 1,3,5-trioxocane synthesis followed by rare sugars synthesis.

Advances in Pd-catalyzed C-C bond formation in carbohydrates and their applications in the synthesis of natural products and medicinally relevant molecules

Advances in the Pd-catalyzed synthesis of C-glycosides and branched sugars are summarized herein and the strategies are categorized based on named reactions or types of sugar moieties involved in the reactions. These include cross-coupling reactions, C-H activations, and carbonylative cross-coupling reactions. Applications of Pd-catalyzed C-glycosylation reactions are discussed in the synthesis of natural products and biologically active molecules such as bergenin, papulacandin D, and SGLT2-inhibitors. Important mechanistic cycles are drawn and the mechanisms for how Pd-activates the sugar moieties for various coupling partners are discussed. The directing group-assisted C-glycosylation and some intramolecular C-H activation reactions are also included.

Synthesis and Structural Characterization of 1-(E-1-Arylpropenon-3-yl)-3,4,6-tri-O-benzyl-d-glucals and Their Transformation into Pentasubstituted (2R,3S,4R)-Chromanes via Pd-Catalyzed Cross Dehydrogenative Coupling Reaction

We have developed an efficient methodology for the synthesis of (2R,3S,4R)-2-hydroxymethyl-3,4-dihydroxy-6-aryl-7-aroylchromanes in which the chirality at the C-2, C-3, and C-4 positions is being drawn from C-glucopyranosyl aldehyde, which in turn can be efficiently synthesized from d-glucose. Thus, the synthesis starts with the transformation of sugar aldehyde into 1-(E-1-arylpropenon-3-yl)-3,4,6-tri-O-benzyl-d-glucals using Claisen-Schmidt type condensation reaction with different acetophenones and then to 1,2-disubstituted glucals via Pd(II)-catalyzed cross dehydrogenative coupling reaction, which in turn has been efficiently converted into (2R,3S,4R)-chromanes via 6π-electrocyclization and in situ dehydrogenative aromatization.

Versatility of glycals in synthetic organic chemistry: coupling reactions, diversity oriented synthesis and natural product synthesis

Glycals, 1,2-unsaturated sugar derivatives, are versatile starting materials for the synthesis of natural products and the generation of novel structural features in Diversity Oriented Synthesis (DOS). The versatility of glycals in synthesis emanates, among others, from the presence of the ring oxygen and the enol-ether type unsaturation, the different types of stable conformations they can adopt depending on the nature of the protecting groups present and the ease with which the protecting groups of the three hydroxy groups could be tailored to suite for a desired manipulation. This review summarizes the literature on the different transformations of the endo glycals into biologically relevant compounds such as chromans, thiochromans, chromenes, thiochromenes, peptidomimetics, bridged benzopyrans etc., as well as on the use of glycals as chiral building blocks for the synthesis of various natural products such as aspicilin, reblastatin, diospongins, decytospolides, osmundalactones, paclitaxel, isatisine, d-fagomine, and spliceostatin, reported post 2014.