Hexaphenylbenzene as a rigid template for the straightforward syntheses of "star-shaped" glycodendrimers

Original glycodendrimers emanating from propargylated hexaphenylbenzene cores and containing up to 54 peripheral sugar ligands have been synthesized by Cu(I)-catalyzed [1,3]-dipolar cycloadditions using both convergent and divergent approaches.     

New Insights into the Diels–Alder Reaction of Graphene Oxide

Graphene oxide is regarded as a major precursor for graphene‐based materials. The development of graphene oxide based derivatives with new functionalities requires a thorough understanding of its chemical reactivity, especially for canonical synthetic methods such as the Diels–Alder cycloaddition. The Diels–Alder reaction has been successfully extended with graphene oxide as a source of diene by using maleic anhydride as a dienophile, thereby outlining the presence of the cis diene present in the graphene oxide framework. This reaction provides fundamental information for understanding the exact structure and chemical nature of graphene oxide. On the basis of high‐resolution ¹³C‐SS NMR spectra, we show evidence for the formation of new sp³ carbon centers covalently bonded to graphene oxide following hydrolysis of the reaction product. DFT calculations are also used to show that the presence of a cis dihydroxyl and C vacancy on the surface of graphene oxide are promoting the reaction with significant negative reaction enthalpies.     

Reactions of Podophyllotoxin with DDQ

Introduction 2, 3-Dichloro-5, 6-dicyanobenzoquinone (DDQ) can react with lignans of the mono- arylidene-butyrolactone1, aryltetralin2, dibenzylbutane3 and aryltetralin-butyrolactone4,5 series. We have studied the reactions of this reagent with podophyllotoxin 1, which is a well-known natural product on account of its long history of use in folk medicine and the biological activity of its many derivatives6. In particular, derivatives of 4-demethyl epipodophyllotoxin are used in cancer chemo…