Mild Palladium‐Catalyzed Cyanation of Unprotected 2‐Iodoglycals in Aqueous Media as Versatile Tool to Access Diverse C2‐Glycoanalogues

Abstract

Access to unprotected 2‐cyano‐glycals via a mild palladium‐catalyzed cyanation of protecting groups‐free 2‐iodoglycals in aqueous media has been developed. Diverse glycal substrates including disaccharide‐type were successfully obtained in good to excellent yields. These unprotected 2‐cyano‐glycal scaffolds were successfully derivatized to different C2‐glycoanalogues.

Glycosamine Derivatives through Metal‐Catalyzed C−N Bond Formation on Protected and Unprotected 2‐Iodoglycals

“…This trend was expected since the same selectivity was observed before by Davis et al . and in the reduction of our previously described C2 ‐cyano‐glycals [9e,w] . Hydrogenolysis in the same conditions of protecting group‐free compound 2 m was supposed to lead to the same 3 a structure, but surprisingly, no traces of 3 a was obtained in the crude, where no distinguishable structures were observed.…”

“…One example of protecting group‐free d ‐iodoglucal was presented but in a modest yield. It should be noticed that the use of protecting group‐free 2‐iodoglycals in metal‐catalyzed cross‐couplings is scarce [9h,w] . Herein, we present a nickel/copper‐catalyzed amidation methodology of both protected and protecting group‐free 2‐iodoglycals as a new route to the synthesis of d ‐mannosamine and d ‐talosamine derivatives (Scheme 1).…”

Synthesis of unprotected glyco-alkynones via molybdenum-catalyzed carbonylative Sonogashira cross-coupling reaction

“…Inspired by this chemistry and continuing a research program in our laboratory devoted to the synthesis of biologically relevant C2-substituted glycals, 10 we questioned whether Mo-catalyzed carbonylative coupling reactions could deliver carbonyl-containing glycals under Pd-free conditions from 2-iodoglycal electrophiles. Moreover, by eliminating palladium from the reaction medium, we wondered if unprotected 2-iodoglycals could be used as electrophiles, 11 which would represent a major improvement from previous reports ( Scheme 2A ). 10,12 …”

Acetic Anhydride–Acetic Acid as a New Dehydrating Agent of Aldoximes for the Preparation of Nitriles: Preparation of 2-Cyanoglycals

“…The nitrile functional group can be transformed into various 2-C branched sugar derivatives and glycomimetics. 25 Furthermore, with the advance of C-H activation and transitionmetal-catalyzed coupling reactions, the ready availability of novel ,-unsaturated systems such as the 2-cyanoglycals 2a are crucial to expand the scope and diversity of these reactions. Despite their potential, there is only one low-yielding (<42%) method reported for the synthesis of 2-cyanoglycals that involves the reaction of glycals with chlorosulfonyl isocyanate.…”