In connection with studies on the biosynthesis of the isocyclic ring E in chlorophyll a (l), the magnesium (I1) 2, 4divinylporphyrin 0-keto ester 8 and hydroxypropionate 6 have been synthesized. The key porphyrin intermediate 36 in these syntheses was obtained most efficiently by cyclization of a l'-methyl-8'-unsubstituted a, c-biladiene dihydrobromide 31 in hot o-dichlorobenzene. An alternative route through copper (I1)-promoted cyclization of a ...
