Preparation and Absolute Configuration of SomeIris Essential Oil Constituents of the 5-methylsafranic-acid series
作者:Christian Chapuis、Karl H. Schulte-Elte
DOI:10.1002/hlca.19950780116
日期:1995.2.8
cyclization of (+)-(Z)-6 to (−)-trans-8a (Scheme 2), followed by a diastereoselective epoxidation to (+)-11 gave, via acid-catalyzed dehydration of the intermediate allylic secondary alcohol (−)-12, the same ester (+)-13a (Scheme 3), but with poor optical purity (13% ee), due to an initial rapid [1,2]-H shift. The absolute configuration of (−)-16a–c was confirmed by chemical correlation with (−)-trans-19 (Scheme
通过(-)-(5 S)-9a通过(-)-(5 S)-9a获得β-二烯酸(+)-(5 S)-13a(ee值为86%;α和β分别与α-和β-丙酮相同)烯丙基叔醇(+)-(1 S,5 S)-15 /(+)-(1 R,5 S)-15(图3)的非对映异构体混合物的酸催化脱水作用。延长的处理通过[1,5] -H转变为α-异构体(-)-(R)-16a而产生纯净的异构化,而外消旋化程度很小(76%ee;方案4)。相反,SnCl 4( - (+) -催化的环化反应立体有择Ž) - 6到( - ) -反式-图8a(流程2)中,随后一非对映选择性环氧化,以(+) - 11得到,经由中间烯丙基次级的酸催化脱水醇(-)- 12,相同的酯(+)- 13a(方案3),但是由于初始的快速的[1,2] -H位移而具有较差的光学纯度(13%ee)。( - ) -的绝对构16a至16c,确认通过化学相关性与( - ) -反式-