New strategies for the synthesis of biologically important tetrapyrroles. The "B,C + D + A" approach to linear tetrapyrroles.J Org Chem. 2000 Jan 14; 65(1):205-13.JO
Linear tetrapyrroles related to phytochrome (1) were prepared in enantiospecific fashion by a new strategy beginning with ring-B,C synthons of type 19 (bis-iododipyrrins). Rings A and D were elaborated by Pd(0)-mediated coupling of 19a with the appropriate alkyne acid or amide derivatives 9 and 20, followed by intramolecular cyclization (method C: BC + D + A --> ABCD).