The invention provides
pyrrolidine compounds, salts thereof, applications of the compounds or the salts thereof in nuclear magnetic probes and medicines, a
reagent, and a
medicine. The
benzamide methylpyrrolidine compounds have a
chemical structure represented by general formula (I); and in the formula (I), R<1> is selected from a
methyl group, an
ethyl group, a methoxy group, an ethoxy group and
halogen, R<2> is selected from a
methyl group, an
ethyl group, a methoxy group, an ethoxy group and
halogen, R<3> is selected from C1-5
alkyl groups and H, X<1> is selected from C1-10 alkylene groups or is deleted, X<2> is selected from -(CH2CH2O)n- (n is 1-5) or is deleted, X<3> is selected from C1-5
alkyl groups, X<4> is selected from
oxygen,
sulfur and a
methylene group, and Ln is selected from Gd and Eu. The compounds have a
gadolinium and
europium chelating structure formed by combining with a
dopamine D2
receptor and depending on intramolecular chelating groups, and specifically enhance the contrast of
dopamine D2
receptor expression tissues on images in
magnetic resonance imaging.