Synthesis of 4- and 10-deuterated neryl and geranyl-β-D-glucosides and their use in corroboration of a mechanism proposed for the fragmentation of heterosides in tandem mass spectrometry

In order to corroborate a mechanism proposed for the fragmentation of the molecular ion of heterosides, involving a hydride migration from the aglycone to the osidic unit, the 4-[2H2]-10-[2H3]-labelled neryl and geranyl-β-D-glucosides have been synthesised. Deuterated ketone was prepared in >99% isotopic abundance by base catalysed exchange with [2H2]-water, and was reacted under Wittig-Horner conditions furnishing the corresponding α,β-unsaturated esters. Selective reduction of the ester group can be performed with DIBA1-H, whereas LiA1H4 give a secondary reduction of the C = C double bond. The published procedure for the β-D-glucosidation of alcohols has been modified in order to optimise conditions on the deuterated nerol and geraniol. By comparison of collision spectra (NICI/CAD) of pure deuterated and undeuterated neryl and geranyl-β-D-glucosides, the proposed fragmentation mechanism is fully corroborated. (author)