AbstractIn order to corroborate a mechanisms proposed for the fragmentation of the molecular ion of heterosides, involving a hydride migration from the aglycome to the osidic unit, the 4‐[2H2]‐10‐[2H3]‐labelled neryl and geranyl‐β‐D‐glucosides9and10have been synthesised.Deuterated ketone1was 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 esters3and4.Selective reduction of the ester group can be performed with DIBAl‐H, whereas LiAlH4give a secondary reduction of the CC double bond.The published procedure (13) for the β‐D‐glucosidation of alochols 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 fragmen