Benzomalvin G and H, an Atropisomeric Pair of Dimethoxylated Quinazolinobenzodiazepine Alkaloids Produced by Aspergillus fumigatiaffinis

Abstract

Aspergillus and Penicillium species produce a variety of quinazolinobenzodiazepine (QBD) alkaloids by using different biosynthetic gene clusters (BGCs). During the course of metabolome analysis of Aspergillus fumigatiaffinis IFM55214, we discovered an atropisomeric pair of QBD natural products, benzomalvin G (1) and H (2), that are produced by this fungus. The isomer 1 was favored in organic solvents, and 2 was favored in aqueous solutions. The stereochemistry and conformation of these 2 compounds were determined unambiguously by Marfey’s method and nuclear Overhauser effect (NOE) analysis, respectively. Furthermore, a putative BGC for 1 and 2 (Afben cluster), composed of 3 genes (AfbenX, AfbenY, and AfbenZ) shared between the ben cluster in Aspergillus terreus and 4 additional genes (methyltransferases and oxygenases), was identified in the genome of A. fumigatiaffinis IFM55214.