Glucosinolates are sulfur-containing secondary metabolites found in plants of the Brassicale order. They are precursors of isothiocyanate species, resulting from C–S hydrolysis catalysed by the thioglucohydrolase myrosinase. We describe the synthesis of bifunctional glucosinolate–mannoside glycoconjugates combining both the structural features of a substrate of myrosinase and a ligand of the lectin FimH. We show that these glycoconjugates serve as enzyme substrates and that myrosinase can indeed hydrolyze the glucosinolate moiety with affinities (K_M, V_max) comparable to the natural substrates glucomoringin and sinigrin. This enzymatic hydrolysis of the thioglycosidic bond led to the efficient formation of an isothiocyanate which was assessed by the formation of the corresponding dithiocarbamate derivatives. Finally, we show that our synthetic bifunctional glycoconjugates also serve as FimH ligands where the glucosinolate moiety does not hamper the interaction with the lectin. Our findings set the stage for an original bioconjugation tool, allowing for myrosinase-triggered specific labelling of lectins using glucosinolate glycoconjugates as non-toxic, water soluble isothiocyanate precursors.

The glucosinolate transporters 1/2/3 (GTR1/2/3) from the Nitrate and Peptide transporter Family (NPF) play an essential role in the transport, accumulation, and distribution of the specialized plant metabolite glucosinolates. Due to representing both antinutritional and health-promoting compounds, there is increasing interest in characterizing GTRs from various plant species. We generated seven artificial glucosinolates (either aliphatic or benzenic) bearing different fluorophores (Fluorescein, BODIPY, Rhodamine, Dansylamide, and NBD) and investigated the ability of GTR1/2/3 from Arabidopsis thaliana to import the fluorescent glucosinolates (F-GSLs) into oocytes from Xenopus laevis. Five out of the seven F-GSLs synthesized were imported by at least one of the GTRs. GTR1 and GTR2 were able to import three F-GSLs actively above external concentration, while GTR3 imported only one actively. Competition assays indicate that the F-GSLs are transported by the same mechanism as non-tagged natural glucosinolates. The GTR-mediated F-GSL uptake is detected via a rapid and sensitive assay only requiring simple fluorescence measurements on a standard plate reader. This is highly useful in investigations of glucosinolate transport function and provides a critical prerequisite for elucidating the relationship between structure and function through high-throughput screening of GTR mutant libraries. The F-GSL themselves may also be suitable for future studies on glucosinolate transport in vivo.

The 1,3-oxazolidine-2-thiones (OZTs) are important chiral molecules, especially in asymmetric synthesis. These compounds serve as important active units in biologically active compounds. Herein, carbohydrate anchored OZTs were explored to develop a copper-catalyzed C-S bond formation with aryl iodides. Chemoselective S-arylation was observed, with copper iodide and dimethylethylenediamine (DMEDA) as the best ligand in dioxane at 60–90 °C. The corresponding chiral oxazolines were obtained in reasonable to good yields under relatively mild reaction conditions. This approach is cheap, as using one of the cheapest transition metals, a simple protocol and various functional group tolerance make it a valuable strategy for getting S-substituted furanose-fused OZT. The structures of the novel carbohydrates were confirmed by NMR spectroscopy and an HRMS analysis.