Indium(I) iodide mediated efficient synthesis of selenoglycosides

On-water synthesis of glycosyl selenocyanate derivatives and their application in the metal free organocatalytic preparation of nonglycosidic selenium linked pseudodisaccharide derivatives

Glycosyl selenocyanate derivatives were prepared in very good yield by the treatment of glycosyl halide or triflate derivatives with potassium selenocyanate in water. A variety of selenium linked pseudodisaccharide derivatives were prepared in excellent yield using glycosyl selenocyanates as stable building blocks in the presence of hydrazine hydrate under metal-free organocatalytic reaction conditions.

Sweet Selenium: Synthesis and Properties of Selenium-Containing Sugars and Derivatives

In the last decades, organoselenium compounds gained interest due to their important biological features. However, the lack of solubility, which characterizes most of them, makes their actual clinical exploitability a hard to reach goal. Selenosugars, with their intrinsic polarity, do not suffer from this issue and as a result, they can be conceived as a useful alternative. The aim of this review is to provide basic knowledge of the synthetic aspects of selenosugars, selenonium salts, selenoglycosides, and selenonucleotides. Their biological properties will be briefly detailed. Of course, it will not be a comprehensive dissertation but an analysis of what the authors think is the cream of the crop of this interesting research topic.

Glycosyl selenoacetates: versatile building blocks for the preparation of stereoselective selenoglycosides and selenium linked disaccharides

Glycosyl selenoacetate derivatives were prepared by the treatment of glycosyl halide with potassium selenocyanate followed by acetylation of in situ generated glycosyl selenols in one pot. A variety of selenoglycosides and selenium linked disaccharide derivatives were prepared in very good to excellent yields using glycosyl selenoacetates as stable building blocks under mild reaction conditions.

Synthesis of 28a-homoselenolupanes and 28a-homoselenolupane saponins

A practical synthesis of 28a-homo-28a-selenolupane triterpenes and the corresponding selenosaponins containing d-mannose, l-arabinose, l-rhamnose, and d-idose moieties is described. Selenium containing triterpenes were obtained from the readily available 3-O-allyl-homobetulin mesylate by nucleophilic substitution with the selenocyanate ion which upon reduction of the -SeCN group afforded the free selenol. Glycosylation using classical Schmidt donors gave 1,2-trans selenosaponins as the main product as well as minute amounts of 1,2-cis isomers. This is one of the very few examples of the synthesis of selenoglycosides by direct glycosylation of free selenols. The studied selenol showed high resistance to air oxidation resulting in good stability during the synthesis of selenolupane derivatives. Cytotoxic activities of new homoselenolupane derivatives were also evaluated in vitro and revealed that some triterpenes exhibited an interesting profile against human cancer cell lines.

Expanded potential of seleno-carbohydrates as a molecular tool for X-ray structural determination of a carbohydrate-protein complex with single/multi-wavelength anomalous dispersion phasing

Seleno-lactoses have been successfully synthesized as candidates for mimicking carbohydrate ligands for human galectin-9 N-terminal carbohydrate recognition domain (NCRD). Selenium was introduced into the mono- or di-saccharides using p-methylselenobenzoic anhydride (Tol2Se) as a novel selenating reagent. The TolSe-substituted monosaccharides were converted into selenoglycosyl donors or acceptors, which were reacted with coupling partners to afford seleno-lactoses. The seleno-lactoses were converted to the target compounds. The structure of human galectin-9 NCRD co-crystallized with 6-MeSe-lactose was determined with single/multi-wavelength anomalous dispersion (SAD/MAD) phasing and was similar to that of the co-crystal with natural lactose.

Convenient syntheses of 1,2-trans selenoglycosides using isoselenuronium salts as glycosylselenenyl transfer reagents

Se-glycosyl-isoselenuronium salts such as three and four which can be prepared in one high-yielding step from acetohalogeno sugars proved to be convenient starting materials for the syntheses of a variety of selenoglycosides. Reaction with (ar)alkyl halides proceeds under mild conditions, in short time, at room temperature to afford the corresponding selenoglycosides in good yields. Aryl halides react to appreciable extent only if bearing activating nitro groups on the aromatic ring. Reactions with acylating reagents such as acetic anhydride and benzoyl chlorides furnished anomeric selenoesters some of which were recently proposed as starting compounds for alternative selenoglycoside syntheses. Selenodisaccharides with two different monosaccharide units could also be prepared via reactions of glycosyl-isoselenuronium salts with monosaccharide derivatives bearing primary or secondary triflate groups.

Stereoselective synthesis of beta-phenylselenoglycosides from glycals and rationalization of the selenoglycosylation processes

Beta-phenylselenoglycosides have been efficiently and stereoselectively synthesized by direct oxidative glycosylation of benzenselenolate (PhSe(-)) with glycals. A rationalization of the presently described beta-selectivity and the opposite alpha-selectivity reported by Danishefsky in the ring-opening of epoxy glycals with benzeneselenol (PhSeH) is proposed.