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Palladium catalysed ligand free direct dehydrogenative C-3 alkenylation of pyrones and unprotected pyridones from unactivated alkenes is reported. The process is highly regio- and chemoselective. A wide variety of alkene partners reacted to broaden the substrate scope of the process. The effect of the C-3 substituent on the rate of reaction is also studied.

The stereochemistry of this arylation reaction is controlled by the configuration at C3 of the glycal.

A diastereoselective, metal-free, one-pot domino synthetic strategy was developed for the transformation of glycals into new chiral scaffolds. Optimization of the reaction conditions to exclude normal Ferrier products, characterization of the new entities, and a plausible mechanism were investigated.

A series of glycosyl donors such as glycals (I) and anomeric acetals (IV) are tested towards an alkynyl zinc reagent obtained from alkynes (II), zinc dust, and ethyl bromoacetate.

Cyclic molecular frameworks, especially the benzannulated medium-sized and macrocyclic ring (BMR) systems, constitute an integral component of a large number of biologically significant natural or synthetic molecules. Many of these BMR compounds are either approved as drugs or have reached the late developmental stages in clinical trials. Such cyclic systems have been shown to possess great potential, especially in the discovery of new anticancer leads. Efforts from synthetic chemists have led to the development of elegant new strategies for the construction of BMR scaffolds of medicinal importance. This review intends to highlight the importance of benzannulated medium-sized and macrocyclic rings (BMRs) and the strategies developed over the years for their synthesis.

Anomeric gem-diallylation, mono-β-crotylation and mono-β-propargylation of sugar 1,5 and 1,4 lactones have been achieved under Barbier reaction conditions using Zn powder and a catalytic amount of TMSCl as an activator. Ring closing olefin metathesis of the synthesized gem-diallyl derivatives furnished C-spiro cyclopentene glycosides. Finally, the cyclopentene rings were converted into carbohydrate based tricyclic morpholine fused triazole glycoconjugates as potential SGLT2 inhibitors.

A highly regio- and diastereo-selective synthesis of halogenated C-vinyl glycosides has been achieved from glycals and unactivated aryl acetylenes in the presence of halogenated Lewis acids via a tandem glycosylation–halogenation reaction. The Lewis acid used served the dual purpose of activating the allylic acetoxy group of glycals and serving as halogen source for Markovnikov addition across the triple bond, which makes the process atom economic. The synthesized glycosyl vinyl halides have been used as precursors for various Pd catalyzed C–C cross coupling reactions.

A highly stereoselective rapid C-glycosylation reaction has been developed between glycal and unactivated alkynes in the presence of coppertriflate and ascorbic acid at low catalyst loading and at room temperature. A wide variety of glycals and aryl acetylenes participate in the reaction smoothly. TfOH generated during the reduction of Cu(OTf)2 by ascorbic acid may be the active catalyst for the glycosylation.

A regioselective high yielding monochloro substitution (chlorohydrin formation) via Mitsunobu reaction is reported. In carbohydrates and sterically hindered non-sugars, only the primary hydroxyl group is chlorinated, whereas in the non-sugar 1,2- and 1,3-alcohols, predominantly the secondary chloride substitution occurs. The versatile methodology provides indirect access to epoxides with the retention of configuration, as against conventional Mitsunobu reaction which generates epoxides with inversion. The methodology was successfully used as a key step in the synthesis of optically active diastereoisomers of the antidepressant drug reboxetine from (R)-2,3-O-cyclohexylidene-D-glyceraldehyde in ∼43% overall yields.

The synthesis of 8-, 9-, 10-, 11-, and 13-membered ring compounds having a carbohydrate ring fragment is established by intramolecular Sonogashira and Heck coupling reactions.

This method uses Mitsunobu conditions and trimethylsilyl azide to substitute primary alcohol moieties of carbohydrates with azide groups while secondary alcohol moieties are silylated.

The advantages of the title reaction are a high regioselectivity, the use of a broad range of substrates and a mild, inexpensive, and nontoxic catalyst, functional-group tolerance, mild reaction conditions, scalability (20 g), easy handling, and a wide application range.

A variety of furanoses and pyranoses (14 examples) bearing a bromobenzyl and a terminal alkynyl group undergo the reaction in the presence of a heterogeneous basic alumina-supported palladium catalyst and CuI as co-catalyst to give benzannulated 10- to 13-membered macrocycles containing the carbohydrate moiety.

Substitution of Ni for In in InTaO4 is reinvestigated by synchrotron X-ray and neutron powder diffraction, diffuse reflectance spectroscopy, XANES, and magnetic susceptibility measurements, providing insights into its previously reported photoactivity.

A convenient and efficient method for selective replacement of the primary hydroxyl groups of sugars by chlorine with concomitant O-formylation, compatible with the presence of a variety of functional groups, has been developed using the Vilsmeier–Haack reaction. Sugars having free primary hydroxyl groups mostly afforded the chloro-O-formylated product while sugars devoid of primary hydroxyl groups yielded only O-formylated products.

Lewis acid mediated one-pot transformation of d-glucal in the presence of nucleophiles leads to the formation of racemic α-substituted α-hydroxymethyl furfuryl derivatives, versatile synthons for biologically active molecules. Transformations using O-, S-, C-, and N-nucleophiles could be achieved readily under mild and scalable conditions. Indium triflate proved to be the catalyst of choice in terms of conversion and regioselectivity.

A novel, highly stereoselective method for O-glycosylation of glycals and glycosylbromides is developed using orthoformates as acceptors in the presence of InCl 3 to afford the corresponding O -glycopyranosides in 66–94% yield. Both perbenzyl and peracetyl glycals afford the corresponding 2,3-unsaturated-O-glycosides with high α-selectivity. Stoichiometric amounts of orthoformates are sufficient to bring about this transformation instead of large excesses of alcohols.