Passing (H2) Gas Concise syntheses of the natural products brosimones A and B using sequential dehydrogenative Diels-Alder (DHDA) cycloadditions are reported. The syntheses employ either Pt/C-cyclopentene or DDQ to effect dehydrogenation of prenylchalcone substrates in combination with silver nanoparticles (AgNP’s) to promote subsequent Diels-Alder cycloadditions.