Patent ID: 7195751

Claim:
A compound of formula: or a salt thereof, wherein, each carbon of the heterocyclic ring has the formula C(J) 2 ; W is NH, N—R 1 , N—R 2 , P—R 1 , P—R 2 , O, C or S; each J is the same or different and is H, deuterium (D), R 1 , OR 1 , SR 1 , NHR 1 , N(R 1 ) 2 , fluorine, chlorine, bromine or iodine; Z is O, S, NH or NR 1 ; and LG is an alcohol or thiol leaving group selected from the group consisting of: wherein, X′ is O or S; R 1 is the same or different and is an alkyl group comprising one to eight carbon atoms which may optionally contain a heteroatom or a substituted or unsubstituted aryl group wherein the carbon atoms of the alkyl and aryl groups independently comprise linked hydrogen, deuterium and/or fluorine atoms; and R 2 is an amino alkyl, hydroxy alkyl, thio alkyl group or a cleavable linker that cleavably links the reagent to a solid support wherein the amino alkyl, hydroxy alkyl or thio alkyl group comprises one to eight carbon atoms, which may optionally contain a heteroatom or a substituted or unsubstituted aryl group, and wherein the carbon atoms of the alkyl and aryl groups independently comprise linked hydrogen, deuterium and/or fluorine atoms; and wherein the compound is isotopically enriched with one or more heavy atom isotopes.