Fatty ester Δ-2 heterocycles were prepared in good yields and excellent regioselectivity from 1,3-dipolar cycloaddition reactions between methyl 10-undecenoate and nitrile oxides. This methodology provides convenient access to the methyl esters of margaric (4b) and stearic (4c) acids in 63–66% yield that contain the isoxazoline heterocycle between C-10 and C-12. These fatty heterocycle compounds are synthesized in a one-pot sequence in which methyl 10-undecenoate is used to trap the reactive nitrile oxide intermediates that are generated by reacting aldoximes with aqueous sodium hypochlorite and a catalytic amount of triethylamine or by directly reacting hydroximic acid chlorides with a stoichiometric amount of base. The fatty ester Δ2-isozazoline heterocycles represent a versatile synthon that may be useful to obtain oleochemicals with potentially new and interesting properties not easily accessible by other methods.