Chemistry of Novel Compounds Possessing Multifunctional Carbon Atoms. X. Synthetic Studies of Efflcient and Practical Chiral Derivatizing Agents Based on the .ALPHA.-Cyano-.ALPHA.-fluorophenylacetic Acid Structure.
作者:Yoshio TAKEUCHI、Hidefumi IWASHITA、Kohji YAMADA、Mayumi GOTAISHI、Noriyuki KUROSE、Toru KOIZUMI、Kuninobu KABUTO、Tadashi KOMETANI
DOI:10.1248/cpb.43.1668
日期:——
In order to develop efficient chiral derivatizing agents (CDAs) which can be obtained readily in optically active form, synthetic studies of α-cyano-α-fluorophenylacetic acid (CFPA) analogs, 3a-e and CFNA (14a), were made. Carboxylation of 6a-e obtained from 4a-e gave 3a-e in low yield. Alternatively, benzyl cyanides 5b-e were converted successfully to the esters 7b-e, 8b-e, and 9b-e, which were fluorinated with FClO3 to produce the fluoro esters 10b-e, 11b-e, and 12b-d, in good yields. However, the attempted ester cleavage of these compounds did not give 3b-e. Carboxyl group introduction into 5e afforded 13, and fluorination with either F2 or FClO3 gave complex mixtures.Carboxylation of the naphthyl analog 16 obtained from 15 did not give 14a. However, fluorination of 18 derived from 17 proceeded readily to give 19, which was hydrolyzed to produce 14a. Optically active (-)-14a was obtained through enzymatic hydrolysis. The racemic acid 14a was condensed with three representative chiral nucleophiles to give 14b-d. From the 1H- and 19F-NMR spectra of these derivatives, it was concluded that CFNA (14a) is potentially a much better CDA than the well known α-methoxy-α-(trifluoromethyl)phenylacetic acid (MTPA).
为了开发易于获得光学活性形式的高效手性衍生化剂(CDA),我们对 α-氰基-α-氟苯乙酸(CFPA)类似物 3a-e 和 CFNA (14a) 进行了合成研究。由 4a-e 制得的 6a-e 经过羧化后得到 3a-e,但收率较低。另外,苄基氰化物 5b-e 成功转化为酯 7b-e、8b-e 和 9b-e,这些酯经 FClO3 氟化后生成氟酯 10b-e、11b-e 和 12b-d,收率较高。然而,尝试对这些化合物进行酯裂解并没有得到 3b-e。在 5e 中引入羧基可得到 13,用 F2 或 FClO3 进行氟化可得到复杂的混合物。然而,由 17 生成的 18 很容易进行氟化反应,生成 19,后者经水解生成 14a。通过酶水解可以得到具有光学活性的 (-)-14a。外消旋酸 14a 与三种具有代表性的手性亲核物缩合,得到 14b-d。从这些衍生物的 1H 和 19F-NMR 光谱中可以得出结论,CFNA(14a)可能是一种比众所周知的 α-甲氧基-α-(三氟甲基)苯乙酸(MTPA)更好的 CDA。