Deciphering fungal metabolon coupling tandem inverse-electron-demand Diels-Alder reaction and semipinacol rearrangement for the biosynthesis of spiro polycyclic alkaloids
摘要
In the intricate process of natural product biosynthesis, a metabolon can enhance metabolic flux by associating sequential enzymes. A fungal metabolon, comprising of flavin-dependent monooxygenase SpeF and P450 monooxygenase SpeG, is identified in the biosynthesis of spiro polycyclic alkaloids (+)-notoamide B and its diastereomer (+)-versicolamide B. Using notoamide E as a substance, SpeF/SpeG metabolon can control the stereoselectivity of its 2,3-epoxidation, followed by hydrogen atom ion at C-17 to generate reactive epoxide tau-mA with dienyl iminium unit. Subsequently, (+)-notoamide B and (+)-versicolamide B are produced via tandem nonenzymatic inverse-electron-demand Diels-Alder reaction and semipinacol rearrangement. This provides the first example of metabolon in the biosynthesis of spiro-prenylated indole alkaloids.