SYNTHESIS OF STERICALLY LOCKED PHYTOCHROME CHROMOPHORES VIA SELECTIVE OXIDATION OF PYRROLE COMPOUNDS

摘要

Phytochromes, photoreceptive chromoproteins, carry a covalently attached linear tetrapyrrole (bilin). Phytochromes mediate various developmental processes of plants and bacteria, through the photoconversion between the red light-absorbing (Pr) and the far-red-light-absorbing (Pfr) forms. In order to determine the stereochemistry of Pr and Pfr forms and elucidate the mechanism of photoconversion, synthesis of sterically locked chromophores could be effective. Toward the synthesis of locked chromophores, it would be ideal if the variou s types of pyrroles could be available from a common pyrrole by simple manipulation. A regioselective oxidation of t-butyl 4-methylpyrrole-2-carboxylates with DDQ was achieved with controlling the three oxidation states depending on the nucleophiles used. One of the oxidation products, an aldehyde, was well applied to synthesis of a sterically locked 15Ea CD-ring and the convergent total synthesis of a 15Ea-PCB derivative was finally achieved. The regioselective oxidation of meso-position of CD-ring component was also investigated and its application to synthesis of a sterically fixed chromophore anchored to meso-position will be also discussed.