85917-84-6Relevant articles and documents
Glycosyl Vinylogous Carbonates as Glycosyl Donors by Metal-Free Activation
Kasdekar, Niteshlal,Walke, Gulab,Deshpande, Kshitij,Hotha, Srinivas
, p. 5472 - 5484 (2022/04/28)
Synthesis of glycoconjugates employs a glycosylation reaction wherein an electrophile and a nucleophile known as a glycosyl donor and an aglycon, respectively, are involved. Glycosyl donors often contain a leaving group at the anomeric carbon that upon reaction with activator(s) results in a highly reactive electrophilic species reported as an oxycarbenium ion contact pair that will then be attacked by the aglycon. Therefore, identification of the correct glycosyl donor and activation protocol is essential for the synthesis of all glycoconjugates. Recently identified [Au]/[Ag]-catalyzed activation of ethynylcyclohexyl glycosyl carbonates is one such versatile method for the synthesis of glycosides, oligosaccharides, and glycoconjugates. In this work, stable glycosyl vinylogous carbonates were identified to undergo glycosidation in the presence of a sub-stoichiometric quantity of TfOH. The reaction is fast and suitable for donors containing both C2-ethers and C2-esters. Donors positioned with C2-ethers resulted in anomeric mixtures with greater selectivity toward 1,2-cis glycosides, whereas those with C2-esters gave 1,2-trans selective glycosides. The versatility of the method is demonstrated by conducting the glycosylation with more than 25 substrates. Furthermore, the utility of the glycosyl vinylogous carbonate donors is demonstrated with the successful synthesis of the branched pentaarabinofuranoside moiety of the Mycobacterium tuberculosis cell wall.
Chemo-selective Rh-catalysed hydrogenation of azides into amines
Galan, M. Carmen,Ghirardello, Mattia,Ledru, Helene,Sau, Abhijit
supporting information, (2020/02/18)
Rh/Al2O3 can be used as an effective chemo-selective reductive catalyst that combines the mild conditions of catalytic hydrogenation with high selectivity for azide moieties in the presence of other hydrogenolysis labile groups such as benzyl and benzyloxycarbonyl functionalities. The practicality of this strategy is exemplified with a range of azide-containing carbohydrate and amino acid derivatives.
Nucleofuge Generating Glycosidations by the Remote Activation of Hydroxybenzotriazolyl Glycosides
Neralkar, Mahesh,Mishra, Bijoyananda,Hotha, Srinivas
, p. 11494 - 11504 (2017/11/10)
Hydroxybenzotriazole is routinely used in peptide chemistry for reducing racemization due to the increased reactivity. In this article, very stable hydroxybenzotriazolyl glucosides were identified to undergo glycosidation. The reaction was hypothesized to go through the remote activation by the Tf2O at the N3-site of HOBt followed by the extrusion of the oxocarbenium ion that was attacked by the glycosyl acceptor. Further, equilibration of the zwitterionic benzotriazolyl species makes the leaving group noncompetitive and generates the nucleofuge that has been reconverted to the glycosyl donor. The reaction is mild, high yielding, fast and suitable for donors containing both C2-ethers and C2-esters as well. The regenerative-donor glycosidation strategy is promising as it enables us to regenerate the glycosyl donor for further utilization. The utility of the methodology for the oligosaccharide synthesis was demonstrated by the successful synthesis of the branched pentamannan core of the HIV1-gp120 complex.
