利用手性酯进行不对称Darzens反应的研究

A STUDY OF ASYMMETRIC DARZENS REACTION WITH CHIRAL CHLORO ACETATE

利用（－）－氯乙酸薄荷酯（１）和（－）－氯乙酸冰片酯（２）与对－甲氧基苯甲醛（３）进行不对称Ｄａｒｚｅｎｓ反应，制得（－）－３－（４－甲氧基苯基）－环氧乙烷－２－羧酸薄荷酯（４）和（－）－３－（４－甲氧基苯基）－环氧乙烷－２－羧酸冰片酯（５），并利用＾１Ｈ－ＮＭＲ谱确定了它们顺反构型，推测了分离得到的ｃｉｓ－４ａ和ｃｉｓ－４ｂ中手性碳（Ｃ２，Ｃ３）的绝对构型。

(-)-menthy1-3-(4-methoxypheny1)-oxirane-2-carboxylate (4) and (-)-borny1-3 -(4-methoxypheny1)-oxirane-2-carboxylate (5) are obtained by asymmetric Darzens condensation of (-)-menthy1 or (-)-borny1 chloro acetate (1 or 2) with p-ansisaldehyde (3) respectively. The trans- or cis-configuration of the products is determined by ~1H -NMR. The absolute configuration of the chirai carbons (C_2, C_3) of the cis-4a and cis-4b are deduced. The trans products mentioned above react with 2-aminothiophenol (6) under cis-opening of the oxirane ring condition to obtain (-)-menthy1-3-[ (2 -aminopheny1)-thio]-2-hydroxy-3-(4-methoxypheny1)-propanoate (7) or (-)-borny1 -3-[(2-aminopheny1)-thio]-2-hydroxy-3-(4-methoxypheny1)-propanoate (8) as the main proudcts. From the data reported in literature the absolute configuration of the chiral carbons (C_2, C_3) of the product is deduced and the ratio between product (2S, 3R) and product (2R, 3S) of the Darzens condensation can be calculated from the separated (2S, 3S) and (2R, 3R) components.