Studies on the synthesis of phytochrome and related tetrapyrroles. Dihydropyrromethenones by photochemical rearrangement of N-pyrrolo enamides

Dihydropyrromethenone 67b, a potential precursor for the synthesis of phytochrome 1, has been prepared in enantiomerically pure form beginning with N-aminopyrrole 64 and the acetylenic acid 62b. The key step involved a 3,5-sigmatropic rearrangement of N-pyrrolo enamide 66b.