a key intermediate , 5 , 5-dimethyl-2-hydroxytetrahydrofuran-2-carboxylic acid ( v ) , prepared from 4-methyl-1 , 4-valerolactone , was dehydrated smoothly to give 5 , 5-dihydrofuran-2-carboxylic acid ( vi ) , through its sodium salt , vi was converted into the corresponding acyl chloride viii , which reacted with cephalotaxine in the presence of pyridine to give ester ix .
C0007066
carboxylic acid
C0014898
ester