CHEMISTRY OF 7-LABDEN-3-BETA,15-DIOL (I) - HOMOCHIRAL SYNTHESIS OF FREGENEDADIOL

7-labden-3beta,15-diol was transformed into its diacetyl or dimethoxy derivatives. By double bond isomerization, allylic oxidation and dehyd rogenation the diacetyl derivative was transformed into a dienone that was aromatized with good yield by methyl loss to afford 3beta,15-diac etoxy-20-nor-5,7,9-labdatrien-7-ol. An analog procedure was used to tr ansform the dimethoxy derivative into 3beta,15-dimethoxy-20-nor-5,7,9- labdatrien- 7-ol. The triflate of the latter was transformed by a cros s-coupling reaction into fregenedadiol dimethyl ether that was demethy lated to afford fregenedadiol.