afforded 2,3-dihydrofurans 3. After catalytic hydrogenation of the C=C bond, followed by reductive removal of the chiral auxiliary, the resulting enantiopure tetrahydrofurans 5 were transformed in two steps into naturally occurring (–)-virgatusin and (+)-urinaligran and two other, nonnatural, tetrasubstituted THF lignans. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
非对映选择性 MnIII 促进的 β-氧代酯 1 与 N-肉桂酰
恶唑烷酮 2 的自由基加成得到
2,3-二氢呋喃 3。在 C=C 键催化氢化后,然后还原去除手性助剂,得到对映纯的
四氢呋喃 5分两步转化为天然存在的 (-)-virgatusin 和 (+)-urinaligran 以及另外两种非天然的四取代 THF
木脂素。(© Wiley-
VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)