Starting from 2, 7-dimethylcycloheptanone, the lactones VII, VIII, XIV, XVI, XX, and XXI have been synthe-sized and their conformation and stereochemistry studied. XVI represents the partial structure of IIa. VI1 and XXI represent the partial structures of 111 and IIc, respectively. Isomerization of &lactone to y-lactone in the presence of acid has been discussed.
