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[摘要]：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 sernicorrins of type 25 derived from 4-alkynoic acids 1. Alkyne acids 1 also played a prominent role in a new 16 pi-electrocyclization route to bacteriochlorins, and in iterative syntheses of semicorrins and secocorrins related to vitamin B-12. 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. |
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