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Abstract 33
D. M. Arnott, P. J. Harrison, G. B. Henderson, Z.-C. Sheng, F. J. Leeper and A. R. Battersby "Synthetic Studies Relevant to Research on Vitamin B12, Part 9. Synthesis of 20-Methyl and 20-Cyano Isobacteriochlorins" J. Chem. Soc., Perkin Trans. 1,1989, 265-278. Full Text lsobacteriochlorins carrying a C-methyl group at C-20 of the macrocycle are important for research on the biosynthesis of vitamin B12. Several different approaches are studied which allow the introduction of a C-20 methyl group into model isobacteriochlorins, the most successful involving the stepwise reduction of a nitrile residue to a methyl group. Successful syntheses are described of two 20- methylisobacteriochlorins and two 20-cyanoisobacteriochlorins. All the routes used depend finally on the photochemical cyclisation of an 18p-electron open-chain precursor.
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