Abstract

91
J. Micklefield, M. Beckmann, R. L. Mackman, M. H. Block, F. J. Leeper and A. R. Battersby
"Haem d₁: Stereoselective Synthesis of the Macrocycle to Establish its Absolute Configuration as 2R,7R"
J. Chem. Soc., Perkin Trans. 1,1997, 2123-2138. Full Text

Although the gross structure of haem d₁ has been established, the absolute stereochemistry at C-2 and C-7 is unknown. An unambiguous stereoselective synthesis of the ester of the metal-free macrocycle corresponding to haem d₁ has been completed which establishes the absolute configuration of the natural cofactor as 2R,7R. Haem d₁ is thus shown to match stereochemically other biologically important macrocycles, e.g. those involved in the biosynthesis of vitamin B₁₂, which are related to isobacteriochlorins and also display 2R,7R configurations. The synthetic sequence used is based on a new procedure for assembly of the western and eastern building blocks and it serves as an efficient general route for construction of isobacteriochlorins.

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