Pyranosides with 2,3-trans carbamate groups exhibit high 1,2-cis selectivity in glycosylation reactions. Using glycosyl donors with N-benzyl 2,3-trans carbamate groups, an anti-Helicobacter pylori oligosaccharide was synthesized in an efficient manner. Moreover, pyranosides with 2,3-trans carbamate groups readily undergo anomerization from the β to the α configuration under mild acidic conditions via endocyclic cleavage. Acyclic cations generated during the endocyclic cleavage reaction were captured using reduction and intramolecular Friedel–Crafts reaction. By exploiting this anomerization, multiply aligned 1,2-trans glycosyl bonds can be transformed to 1,2-cis glycosyl bonds in a single operation.

Aminoglycosides containing a 2,3-trans carbamate group easily undergo anomerization from the 1,2-trans glycoside to the 1,2-cis isomer under mild acidic conditions. The N-substituent of the carbamate has a significant effect on the anomerization reaction; in particular, an N-acetyl group facilitated rapid and complete α-anomerization. The differences in reactivity due to the various N-substituents were supported by the results of DFT calculations; the orientation of the acetyl carbonyl group close to the anomeric position was found to contribute significantly to the directing of the anomerization reaction. By exploiting this reaction, oligoaminoglycosides with multiple 1,2-cis glycosidic bonds were generated from 1,2-trans glycosides in a one-step process.

Glycosyl donors for the preparation of 1,2-cis glycosides of amino sugars have been developed. The 2,3-trans-cyclic-carbamate-carrying glycosyl donors were readily prepared from the corresponding known trichloroethyl carbamate protected amino sugars under standard hydroxy group benzylation conditions. The donors exhibit high 1,2-cis stereoselectivity towards secondary hydroxy group substrates. In the case of primary hydroxy acceptors, high stereoselectivities were achieved with the aid of the dioxane effect. After glycosylation, the carbamate was removed under alkaline conditions. Importantly, these glycosyl donors can be used in polymer-supported and solid-phase synthesis.

2,3-trans-carbamate- and -carbonate-carrying pyranosides were very easily anomerised from the β to the α direction in the presence of a Lewis acid compared to other pyranosides. This reaction is caused by endocyclic cleavage of the pyranosides. Evidence for endocyclic cleavage of conformationally restricted pyranosides in the chair form was obtained by intra- and intermolecular Friedel–Crafts reactions, chloride addition, and reduction of the generated cation. On the other hand, pyranosides with the distorted conformation were never cleaved in an endocyclic manner.