Reagents and methods for labeling terminal olefins

In one aspect, the present invention provides a method for labeling a terminal olefin, the method comprising a step of treating a terminal olefin substrate having the structure: with a labeled ethylene reagent in the presence of a suitable catalyst under suitable olefin metathesis reaction conditions to form a labeled terminal olefin having the structure: wherein RA and RB are independently hydrogen, or an aliphatic, alicyclic, heteroaliphatic, heterocyclic, aryl or heteroaryl moiety, with the proviso that RA and RB are not each hydrogen, or RA and RB taken together with the carbon atom to which they are attached form an alicyclic or heterocyclic moiety; and * denotes the presence of an isotopic label on the terminal carbon atom.