SelectiveN-Sulfation of Glucosamine Derivatives using Phenyl Chlorosulfate in Non-Aqueous Solvent

Synthesis of Spirocyclic Compounds by a Ring-Expansion/Cationic Cyclization Cascade Reaction of Chlorosulfate Derivatives

A novel cascade reaction to prepare spirocarbocyclic compounds from chlorosulfate derivatives has been developed. The process involves an unusual thermal elimination of the chlorosulfate moiety, a ring-expansion reaction, and a subsequent cationic cyclization reaction. Despite the relatively complex skeletal rearrangement, the reaction described here is featured by its operational simplicity, being just a thermal process that does not require additional reagents, catalysts, or additives.

Synthesis of Sultones from Chlorosulfates by a Complex Cascade Reaction Occurring under Mild Thermal Conditions

Chlorosulfate derivatives are interesting reagents that have been traditionally used to get other sulfur-containing compounds by formal nucleophilic substitution of the chlorine atom. This work describes a different mode of reactivity of alkyne-containing chlorosulfates to get sultones, the sulfur analogues of lactones. The complex skeletal rearrangement observed in this transformation is comparable to those intricate processes promoted or catalyzed by organometallic compounds. However, the reaction here described does not require any reagent or additive, being just a thermal process. Computational calculations support a mechanism based on a series of cascade reactions where almost every step is counterintuitive. Some of these steps include original processes related to classical reactions, thus adding complementary views to traditional organic chemistry.

Divergent heparin oligosaccharide synthesis with preinstalled sulfate esters

Traditional chemical synthesis of heparin oligosaccharides first involves assembly of the full length oligosaccharide backbone followed by sulfation. Herein, we report an alternative strategy in which the O-sulfate was introduced onto glycosyl building blocks as a trichloroethyl ester prior to assembly of the full length oligosaccharide. This allowed divergent preparation of both sulfated and non-sulfated building blocks from common advanced intermediates. The O-sulfate esters were found to be stable during glycosylation as well as typical synthetic manipulations encountered during heparin oligosaccharide synthesis. Furthermore, the presence of sulfate esters in both glycosyl donors and acceptors did not adversely affect the glycosylation yields, which enabled us to assemble multiple heparin oligosaccharides with preinstalled 6-O-sulfates.

Orthogonal sulfation strategy for synthetic heparan sulfate ligands

[reaction: see text] An orthogonal sulfation strategy involving six different protecting groups has been developed for generating sulfated carbohydrate libraries based on heparan. Chemoselective cleavage conditions (optimized for a heparan disaccharide) can be performed in the presence of sulfate esters as well as the remaining protecting groups.