An improved general synthetic approach to cis-clerodane diterpenoids. A more efficient total synthesis of (+/-)-6 beta-acetoxy-2-oxokolavenool

The previously developed general synthetic approach to cis-clerodane diterp enoids has been greatly improved using 4-(2-benzyloxy)ethyl-2-cyano-4-methy l-2,5-cyclohexendien-1-one (4) as the starting dienophile. This approach al lows the direct incorporation of an angular methyl group via reductive alky lation of the a-cyano ketone system. The viability of this approach to cis- clerodanes has been demonstrated in the alternative total synthesis of (+/- )-6 beta -acetoxy-2-oxokolavenool (1). (C) 2001 Elsevier Science Ltd. All r ights reserved.