The first synthesis of dasyscyphin B, an antitumoral metabolite obtained from the ascomycete Dasyscyphus niveus, has been achieved starting from commercial abietic acid. The key steps of the synthetic sequence are the diastereoselective α-methylation of a ketoaldehyde, followed by an intramolecular aldol condensation and the further Diels–Alder cycloaddition of a dienol ester. The procedure reported will allow the synthesis of related metabolites functionalized in the A ring.The authors thank the Spanish Ministry of Science and Innovation (project CTQ2009-09932) and the Regional Government of Andalucia (project P11-CTS-7651 and assistance to the FQM-348 group) for financial support. A.F. thanks the Spanish Ministry of Science and Innovation for the predoctoral grant provided