Asperlicin

Using tin triflate, as an effective Lewis acid, and microwaves, direct double cyclizations of bis(anthranilate)-containing tripeptide precursors to afford the total syntheses of 7-substituted quinazolino[3,2-a][1,4]benzodiazepinediones (1a-f), including natural products circumdatin F (1a), sclerotigenin (1b), and asperlicin C (1c), were achieved with good overall isolated yields (23-62%).

Using scandium triflate and microwaves, the direct double dehydrocyclization of anthranilate-containing tripeptides was achieved, affording the total syntheses of (i) quinazolino[3,2-a]benzodiazepinediones (), (ii) diazepino[2,1-b]quinazolinediones (), and (iii) pyrazino[2,1-b]quinazolinediones () with good overall isolated yields (23-43%, 37-47% and 31-56%, respectively). Among the quinazolino[3,2-a]benzodiazepinediones synthesized, (sclerotigenin), (circumdatin F), and (asperlicin C) are natural products.

Members of the asperlicin family of fungal metabolites produced by Aspergillus alliaceus are known potent CCK(A) antagonists. Herein, we report the identification of the gene cluster responsible for directing their biosynthesis. We validate and probe the pathway by genetic manipulation, and provide the first biochemical characterization of the oxidative cyclization en route to the heptacyclic asperlicin E by reconstituting the activity of the FAD depend monooxygenase AspB. This report provides the first genetic characterization of a NRPS assembly line that efficiently activates two anthranilate building blocks and illustrates the remarkably efficient biosynthesis of the complex heptacyclic asperlicin E.