The synthesis of novel hexa-13C-labelled glucosinolates from [13C6]-d-glucose

An isotopically labelled building block, 2,3,4,6-tetra-O-acetyl-1-thio-β-d-[13C6]glucopyranose (4), is obtained from the commercially available [13C6]-d-glucose. This hexa-13C-labelled thioglucose can be employed to make any glucosinolate (8) for use as an internal standard for isotopic dilution LCMS analysis. Herein three typical glucosinolates in their hexa-13C-labelled form: [glucose-13C6]gluconasturtiin, [glucose-13C6]sinigrin and [glucose-13C6]glucoerucin are synthesised by coupling the isotopically labelled thioglucose (4) with the corresponding hydroximoyl chlorides followed by sulfation with pyridine sulfur trioxide and deacetylation with a catalytic amount of potassium methoxide, respectively.