Studies on the terpenoids and related alicyclic compounds. XXVI. Total syntheses of highly oxygenated furanoeremophilanes: (.+-.)-6.BETA.-Hydroxy-1,10-dehydrofuranoeremophilan-9-one, (.+-.)-decompositin, (.+-.)-dihydrodecompositin, (.+-.)-adenostylone, (.+-.)-3.BETA.,6.BETA.-dipropionyloxyeuryopsin-9-one, (.+-.)-3.BETA.,6.BETA.-dihydroxy-10.BETA.