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Synthesis of glucosinolates: Gluconasturtiin (2-Phenylethyl Glucosinolate) and Glucomoringin analogue(4’-O-alpha-D-Mannopyranosyl) Glucosinalbin)

Using the known procedure of Rollin et. al. two different glucosinolates (GLs), gluconasturtiin (found in species belonging to Brassicaceae family), and glucomoringin analogue (not found in nature) were successfully synthesized. Gluconasturtiin, as one of the most widely distributed GLs in the cruciferous vegetables, has been synthesized using aldoxime pathway followed by hydroxamate disconnection. Chlorination of aldoxime by sodium hypochlorite solution afforded the corresponding hydroxyl chloride. Without further purification, this electrophilic acceptor reacted with 1-thio-alpha-D-glucopyranose tetraacetate in the presence of an organic base to produce the anomeric thiohydroxamate intermediate for further reactions of sulphation and deacetylation to gain an expected product gluconasturtiin. A more striking application of the nitrovinyl pathway was the synthesis of the major GL of plant Moringa oleifera, known by its trivial name glucomoringin. This GL is an O-rhamnosylated form of glucosinalbin. Corresponding nitrovinyl derivate, under Lewis acid activation with triethylsilane as a source of the hydride ion, led to the formation of substituted acetohydroxymoil chloride. By syn-addition of 1-thio-alpha-D-glucopyranose thiohydroxamate intermediate was obtained for further reactions of sulphation and deacetylation to produce expected product glucomoringin. Analysis of all the synthesized products and corresponding intermediates was performed using different spectroscopic techniques and methods. Characterization of molecule's mass was done by MSquadrupole - FIA method. IR spectroscopy was used to characterize various functional groups. NMR spectroscopy (1H, 13C, DEPT90, DEPT135, COSY, HSQC) was used to record all C-C and H-H couplings between atoms in synthetized products. HPLC techniques as well as the inverse purification chromatography systems were used to purify all the resulting products.

glucosinolates; gluconasturtiin; glucomoringin; synthesis; NMR

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