Asymmetric Synthesis of a Chiral Building Block for Cyclopentanoids: A Novel Enantioselective Synthesis of Preclavulone A
作者:Giuseppe Zanoni、Alessio Porta、Enrico Brunoldi、Giovanni Vidari
DOI:10.1021/jo061321h
日期:2006.10.1
(R)-cyclopent-2-enecarboxylic acid (15) in excellent yield and high enantiomeric purity (>98% ee). 6-exo-trig atom-transfer radical cyclizations of ((R)-cyclopent-2-enyl)methyl 2-iodoacetate (12) produced exclusively the desired cis-fused δ-lactone (4aR,7aR)-hexahydro-5-iodocyclopenta[c]pyran-3(1H)-one (11), which was subsequently elaborated to hydroxylactone 1 through a stereocontrolled Pd(II)-mediated
羟基内酯(+)-(3a R,4 R,6a S)-4-(羟甲基)-3a,4-二氢-3 H-环戊[ b ]呋喃-2(6a H)-one的一种新的不对称方法(1),已经描述了用于顺式1,2,2-二取代的五元环衍生物(即异前列腺素,茉莉酮酸酯和克拉维酮)的关键合成构件。实现了对三个立体中心的绝对和相对构型的显着控制。因此,使用Trost的不对称烯丙基烷基化策略可确保高度对映体富集的(R)-3-(硝基甲基)环戊-1-烯(13),后者可以平滑地转化为(R)-环戊-2-烯羧酸(15),具有优异的收率和高对映体纯度(> 98%ee)。((R)-环戊-2-烯基)2-碘乙酸甲酯(12)的6 - exo - trig原子转移自由基环化反应,仅产生所需的顺式稠合δ-内酯(4a R,7a R)-hexahydro-5 -iodocyclopenta [ ç ]吡喃-3-(1 ħ) -酮(11),随后将其加工为羟基内酯1通过立体控制的Pd(II)