potassium carbonate in 1-methyl-pyrrolidin-2-one T=20°C; Alkylation; 1.5 h;

1: formic acid methyl ester; (+/-)-(3aR*,5S*,8bS*)-5-hydroxy-8,8-dimethyl-3,3a,4,5,6,7,8,8b-octahydroindeno[1,2-b]furan-2-one With sodium hydride Condensation; 2: (±)-4-bromo-2-methyl-2-buten-4-olide Etherification;