The total synthesis of rel(2,6-Dihydroxy-4-methoxyphenyl)[(1R,5S,6R)-4-methyl-5-(3-methyl-2-buten-1-yl)-6-phenyl-3-cyclohexen-1-yl]methanone [(±)-nicolaioidesin B] a natural product (flavonoid deriv.) that shows preferential cytotoxicity against pancreatic cancer cells under nutrient starvation conditions, is achieved. The key step is a thermally-induced, highly regioselective and diastereoselective Diels-Alder reaction between (E)-N-methoxy-N-(methyl)cinnamide and ocimene under solvent-free conditions. The synthesis of the target compd. was achieved using (1R,5S,6R)-rel-4-methyl-5-(3-methyl-2-buten-1-yl)-6-phenyl-3-cyclohexene-1-carboxaldehyde and 2-bromo-5-methoxy-1,3-bis[[2-(trimethylsilyl)ethoxy]methoxy]benzene as reactants.