The first total synthesis of guajavadimer A, a dimeric caryophyllene-derived meroterpenoid featuring an unprecedented 4–9–6–6–6–9–4-fused ring system, is reported. Key to the approach is the construction of the pyrano[4,3,2-de]chromene core via a cascade of double hetero-Diels–Alderreactions. Practically, a 4-substituted-2,6-dihydroxybenzaldehyde dimethyl acetal serves as an effective surrogate for