Pigmentation, mammalian

The compounds of the t/block elements show a wide range of interesting properties. Some are vital to life. Iron is an essential component of mammalian blood. Compounds of cobalt, molybdenum, and zinc are found in vitamins and essential enzymes. Other compounds simply make life more interesting and colorful. The beautiful color of cobalt blue glass, the brilliant greens and blues of kiln-baked pottery, and many pigments used by artists make use of d-block compounds. 

Hearing, V. J., and Jimenez, M. (1989). Analysis of mammalian pigmentation at the molecular level. Pigment Cell Res. 2 75-85. 

H- 1,4-Thiazines and benzothiazines undergo oxidation to dehydro dimers (83) and (84) which are of considerable interest as they are the parent chromophores of the trichosiderin (trichochrome) pigments which occur in mammalian red hair and in the feathers of some birds (74T2781). In the case of monocyclic thiazines, reagents such as nitrobenzene or picric acid are required, but air oxidation is sufficient in the bicyclic series. It is curious that whereas aerial oxidation of the ester (85) gives both the dehydro dimers (86) and (87), ethyl azodicarboxylate only yields the tautomer (87) <70AC(R)35l). 

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