N.M.R. STUDIES OF BRIDGED RING SYSTEMS: II. UNUSUAL MAGNETIC DESHIELDING EFFECT ON THE BRIDGE METHYLENES OF NORBORNADIENE AND BENZONORBORNADIENE

Proton magnetic resonance spectra of some norbornane derivatives having double bonds and (or) a benzene ring in the skeleton were studied. Differences in the chemical shifts between the bridge methylenes of norbornene and benzonorbornene and that of norbornane result from the diamagnetic anisotropy effect of a double bond or a benzene ring being in good agreement with the values calculated theoretically. However, in the norbornadiene derivatives which have two double bonds or one olefinic double bond with a benzene ring in a part of the skeleton, the signals of their bridge methylenes show extraordinarily larger downfield shifts by about 0.8 p.p.m. than those expected from the additive shielding due to each π-electron system. This anomaly is not observed in bicyclo[2.2.2]octane ring series. A large transannular interaction between two π-electron systems in that system would be a major contribution to the above anomaly.

Experimental hemosiderosis: relationship between skin pigmentation and hemosiderin

Iron (totalling 7.5 mg per mouse in three doses) was injected into hairless mice to determine the relationship between skin pigmentation and hemosiderin deposition. The skin color reached its maximum 24 to 48 hours after the last injection and then gradually faded over the subsequent 8 months. In the skin, hemosiderin granules were present extracellularly between collagen bundles as well as within dermal macrophages, Langerhans cells and indeterminate dendritic cells of the epidermis. A larger amount of iron was deposited in the facial than in the dorsal skin, resulting in darker pigmentation of the former. This study suggests that brownish discoloration of skin in hemochromatosis might be attributable in some degree to accumulation of hemosiderin and that pronounced hyperpigmentation of the face in hemochromatosis might be due to increased activation of melanocytes by a high content of hemosiderin.