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Review | Special issue | Vol 82, No. 2, 2010, pp.1029-1081
Published online, 30th August, 2010
DOI: 10.3987/REV-10-SR(E)6
4-Alkynoic Acids in the Synthesis of Biologically Important Tetrapyrroles

Peter A. Jacobi,* Harry L. Brielmann, Melanie Chiu, Indranath Ghosh, Sheila I. Hauck, Sandra Lanz, Sam Leung, Yongkai Li, Hui Liu, Franzisca Löwer, William G. O’Neal, Douglas Pippin, Elizabeth Pollina, Benjamin A. Pratt, Frédéric Robert, William P. Roberts, Carlos Tassa, and Hui Wang

*6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, U.S.A.

Abstract

In this review an account is given of the author's use of 4-alkynoic acid derivatives in the synthesis of members of the chlorin, bacteriochlorin and corrin classes of macrocyclic tetrapyrroles. In the case of chlorins, we employed a novel "2+2" condensation to prepare both C,D-symmetric and non-symmetric chlorins, made possible by the ready availability of semicorrins of type 25 derived from 4-alkynoic acids 1. Alkyne acids 1 also played a prominent role in a new 16π-electrocyclization route to bacteriochlorins, and in iterative syntheses of semicorrins and secocorrins related to vitamin B12. Mechanistic studies provided insight into the nature of these Pd(0)-catalyzed coupling/cyclization reactions. Finally, we describe enantioselective syntheses of ring-C and ring-D alkyne acids for an ongoing synthesis of cobyric acid.