Efficient Synthesis of the alkyl chains with multiple stereogenic centers

下面所示的两个实验已经成功完成。(1)利用N， o -乙烯基烯醛缩醛建立远端不对称诱导方法研究了由α-甲基-α，β-不饱和亚胺衍生的N， o -乙烯基烯缩醛通过lewis酸介导的醛缩醛与缩醛的立体选择性合成。同样的N， o -缩醛也与醛和过量的TiCl_4反应生成了合合物。已知N， o -缩醛通过与醛和一种等价物TiCl_4反应产生立体选择性抗加合物。因此，我们通过选择TiCl_4的用量，建立了立体发散合成δ-烷氧基-γ-甲基-α，β-不饱和亚胺的方法。手性乙烯烯N， o -缩醛与酸酐反应进行酰化，即1,6 -不对称诱导反应。此外，不含α-甲基的手性乙烯烯N， o -缩醛也进行了远程不对称诱导。(2)具有多个立体中心的聚酮的合成上述远程不对称诱导反应的加合物进行了区域和立体自还原，得到了具有所需立体化学性质的甲基支链脂肪酸。手性乙烯烯N， o -缩醛和α-甲基-α，β-不饱和醛的加合物既有烯丙醇和α，β-不饱和亚胺。利用该加合物，我们实现了区域选择性和立体选择性还原，并建立了还原聚酮链的短步合成方法。

Two subjects shown below have been successfully performed.(1) Development of remote asymmetric induction methodologies by using chiral vinylketene N, O-acetalsThe chiral vinylketene N, O-acetal, derived from α-methyl-α,β-unsaturated imide, was found to give syn adduct stereoselectively by the Lewis-acid mediated aldol reaction with acetals. The same N, O-acetal also gave syn adducts by reaction with aldehyde and excess amount of TiCl_4. This N, O-acetal has already known to afford anti adducts stereoselectively by reacting with aldehyde and one equivalent of TiCl_4.Therefore, we established stereo-divergent synthesis ofδ-alkoxy-γ-methyl-α,β-unsaturated imide by choosing amount of TiCl_4.The chiral vinylketene N, O-acetal has reacted with acid anhydrides to proceed acylation, the 1, 6-asymmetric induction reaction. Additionally, the chiral vinylketene N, O-acetal without the α-methyl group also performed the remote asymmetric induction.(2) Synthesis of polyketide haing multiple stereogenic centersThe adducts of the remote asymmetric induction reaction mentioned above have been submitted to the regio-and stereoselevtive reduction to give methyl-branched fatty acids with desired stereochemistry.The adduct of the chiral vinylketene N, O-acetal and an α-methyl-α,β-unsaturated aldehyde has both allylic alcohol and the α,β-unsaturated imide. Taking advantage of the adduct, we have realized the regio-and stereoselective reduction and established the short step synthesis of reducted polyketide chains.