Tolyporphins L–R: Unusual Tetrapyrroles from a <i>Brasilonema</i> sp. of Cyanobacterium

Abstract

Tolyporphins L-R (<b>2</b>-<b>8</b>) have been isolated from a mixed cyanobacterium-microbial culture. The structures of tolyporphins L and M have been revised to four constitutional isomers, isolated as two mixtures of dioxobacteriochlorins (<b>2</b>/<b>3</b> and <b>4</b>/<b>5</b>). In contrast, tolyporphin P (<b>6</b>) is a fully oxidized tetrapyrrole, while tolyporphins Q and R (<b>7</b> and <b>8</b>) are oxochlorins. X-ray structures are reported for the first time for tolyporphins A (<b>1</b>), R (<b>8</b>), and E (<b>9</b>), revealing unexpected stereochemical variation within the series.