Syntheses of Nostodione A and Half Scytonemins.

Syntheses of nostodione A and half scytonemins have been achieved. Nostodione A was synthesized by oxidation of a compound possessing the 3,4-dihydrocyclopenta[b]indol-2(1H)-one skeleton, which was employed in our scytonemin synthesis. Half scytonemins have been synthesized from the same intermediate by the reaction sequence including reduction to indoline, Pd (0)-catalyzed arylation at the α position of the ketone, and oxidation of both the side chain and the tricyclic core structure. UV-Vis spectra of half scytonemins were compared with that of scytonemin, a UV-absorbing cyanobacterial sheath pigment.