Total synthesis of asperlicin C, circumdatin F, demethylbenzomalvin A, demethoxycircumdatin H, sclerotigenin, and other fused quinazolinones

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 (1a-f), (ii) diazepino[2,1-b]quinazolinediones (2a-e), and (iii) pyrazino[2,1-b]quinazolinediones (3a-e) with good overall isolated yields (23-43%, 37-47% and 31-56%, respectively). Among the quinazolino[3,2-a]benzodiazepinediones synthesized, 1a (sclerotigenin), 1b (circumdatin F), and 1f (asperlicin C) are natural products.