Linear tetrapyrroles related to phytochrome (1) were prepared in enantiospecific fashion by a newstrategy beginning with ring-B,C synthons of type 19 (bis-iododipyrrins). Rings A and D wereelaborated by Pd(0)-mediated coupling of 19a with the appropriate alkyne acid or amide derivatives9 and 20, followed by intramolecular cyclization (method C: BC + D + A → ABCD).
