Diastereo- and Enantioselective Formal Synthesis of (+)-Conagenin via Asymmetric [2,3]-Wittig Rearrangement
作者:Dieter Enders、Michael Bartsch、Jan Runsink
DOI:10.1055/s-1999-3398
日期:1999.2
The formal synthesis of the immunomodulator (+)-conagenin (1) is accomplished in a twelve-step sequence with good overall yield (19%), diastereoselectivity and enantiomeric excess (ds syn = 88%, ee = 91%). Key steps of the synthesis are the asymmetric [2,3]-Wittig rearrangement of crotyloxyacetaldehyde-SAEP-hydrazone (S)-5 and the diastereoselective reduction of methylketone (R,S)-12. The absolute configuration of the (4R)-stereogenic center was determined by 1H NMR NOE-measurements with respect to the known absolute configuration of the (2R,3S)-stereogenic centers of lactone (R,S,R)-14.
免疫调节剂 (+)-conagenin (1) 的正式合成通过十二步顺序完成,具有良好的总产率 (19%)、非对映选择性和对映体过量 (ds syn = 88%,ee = 91%)。合成的关键步骤是巴豆酰氧基乙醛-SAEP-腙(S)-5的不对称[2,3]-Wittig重排和甲基酮(R,S)-12的非对映选择性还原。 (4R)-立体中心的绝对构型通过1H NMR NOE测量相对于内酯(R,S,R)-14的(2R,3S)-立体中心的已知绝对构型来确定。