Taxonomy Driven Discovery of Polyketides from <i>Aspergillus californicus</i>

Abstract

Five new polyketides were isolated from the rare filamentous fungus <i>Aspergillus californicus</i> IBT 16748 including calidiol A (<b>1</b>); three phthalide derivatives califuranones A₁, A₂, and B (<b>2</b>-<b>4</b>); and a pair of enantiomers (-)-calitetralintriol A (-<b>5</b>) and (+)-calitetralintriol A (+<b>5</b>) together with four known metabolites (<b>6</b>-<b>9</b>). The structures of the new products were established by extensive spectroscopic analyses including HRMS and 1D and 2D NMR. The absolute configurations of two diastereomers <b>2</b> and <b>3</b> and the enantiomers (-<b>5</b>) and (+<b>5</b>) were assigned by comparing their experimental and calculated ECD data, whereas the absolute configuration of <b>4</b> was proposed by analogy. Compound <b>1</b> showed moderate activity against methicillin-resistant <i>Staphylococcus aureus</i>.