Efficient Synthesis of the alkyl chains with multiple stereogenic centers

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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.