(±)-Phycocyanobilin and its derivatives bearing a photoreactive group at D-ring were first synthesized by the development of a new and convenient method for the preparation of A-ring, transesterification for propanoic acid side-chains of the pyrrole derivative common to B- and C-rings, and deprotection of allyl ester side-chains with a palladium catalyst to avoid migration of exocyclic olefin of A-ring.

C/D-Ring components of phycobilin derivatives bearing a photoreactive group at D-ring were regioselectively synthesized by applying our original synthetic reactions such as acid-catalyzed rearrangement of 2-tosyl group of 3,4-disubstituted 2-tosylpyrroles to 5-position, regioselective preparation of 3,4-disubstituted 5-tosylpyrrolinones, and their Wittig-type new coupling reaction with 2-formyl pyrrole.

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Controlled Synthesis of C/D-Ring Components of Phycobilin Derivatives Bearing a Photoreactive Group at D-Ring.-The key step in the synthesis of the title compounds such as (XI) is the Wittig type new coupling reaction of tosylpyrrolinones [cf. (IX)] with 2-formylpyrrole (X). -(MASUKAWA, T.; KATO, H.; KAKIUCHI, T.; JAYASUNDERA, K. P.; KINOSHITA, H.; INOMATA, K.; Chem. Lett. (1998) 5, 455-456; Dep. Chem., Fac. Sci., Kanazawa Univ., Ishikawa, Kanazawa 920, Japan; EN)