Conversion of 3-methoxy-4, 5-methylenedioxybenzaldehyde into (2RS, 3SR, 4RS)-2- methoxycarbonyl-4-(3-methoxy-4, 5-methylenedioxyphenyl)-3-methyl-4-butanolide (11) was carried out in seven steps via 1-acetoxy-1-(3-methoxy-4, 5-methylenedioxyphenyl) ...