Asymmetric biomimetic oxidations of phenols using oxazolidines as chiral auxiliaries: the enantioselective synthesis of (+)- and (−)-dehydrodiconiferyl alcohol
Stereoselective bimolecular radical coupling reactions of phenylpropenoid phenols are described. Evans's 2-oxazolidinone 11a–d derivatives of ferulic acid were prepared and oxidized to give dimeric benzofuran neolignan structures 12–13a–d in 40–50% overall yields. The chiralphenols were dimerized either enzymatically with hydrogen peroxide and horseradish peroxidase (HRP) or with silver oxide. The
Stereoselective bimolecular radical coupling reactions of phenylpropenoid phenols are described. Oppolzer's camphor sultam 1 and Evan's 2-oxazolidinone 2a-d derivatives of ferulic acid were prepared and oxidized to give dimeric benzofuran neolignan structures 11 in 40-50% overall yields. The chiral phenols were oxidized either enzymatically with hydrogen peroxide and horseradish peroxidase (HRP) or by silver oxide. The observed enantioselectivity after reductive cleavage of chiral auxiliaries gave the neolignan dehydrodiconiferyl alcohol 12 in 18-84% e.e.