ORGN 74 |
| A novel photochromically-controlled, activatable T1-weighted magnetic resonance imaging (MRI) contrast agent was synthesized and characterized. The compound tethers a spiropyran(SP)/merocyanine(MC) motif to a Gd-DO3A moiety. When in dark, the contrast agent is in its MC form and has higher relaxivity (r1: 3.5604 mM-1s-1). After irradiation with visible light, the contrast agent experiences a color change due to the partial isomerization to SP form and has lower relaxivity (r1: 3.1856 mM-1s-1). The decrease of relaxivity in SP isomer may be due to the “indoline cap” on Gd3+, which prevents the water molecules from accessing the metal cation, thus inhibits MRI contrast enhancement. The result indicates that the relaxivity decrease is related to the extent of isomerization to SP form. The potential ability to turn this type of contrast agent “ON” and “OFF” would be a useful addition to the recent reports of biochemical reporter contrast agents. |
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Process R&D, Physical Organic Chemistry, Heterocycles, Aromatics, Metal-Mediated Reactions
8:00 PM-10:00 PM, Sunday, March 25, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Organic Chemistry |