Lipase-Catalyzed Asymmetric Synthesis of Desprenyl-carquinostatin A and Descycloavandulyl-lavanduquinocin
作者:Tominari Choshi、Yoshinari Uchida、Yukiko Kubota、Junko Nobuhiro、Mitsuhiro Takeshita、Takushi Hatano、Satoshi Hibino
DOI:10.1248/cpb.55.1060
日期:——
An asymmetric synthesis of the core carbazole structure, 6-desprenyl-carquinostatin 3 and 6-descycloavandulyl-lavanduquinocin 3, toward a total synthesis of carquinostatin A (1) and lavanduquinocin (2), has been established. Lipase QLM (Meito) catalyzed enantioselective acetylation of the racemic alcohol 6 gave the (−)-acetate 7 and the (+)-alcohol 6 with high enantioselectivity. The absolute stereochemistry of the (−)- and (+)-alcohol 6 have been determined to be R- and S-configurations, respectively, by the advanced Mosher method. In the same manner, the (−)-acetate 13 and the (+)-alcohol 12 have been obtained from the racemic alcohol 12. The (R)-(−)-acetate 13, derived from the (R)-(−)-acetate 7, was the same as the (−)-acetate 13, which has been determined to be (R)-configuration. Oxidation of the (R)-(−)-acetate 13 followed by hydrolysis afforded (R)-(−)-6-desprenyl-carquinostatin [and (R)-(−)-6-descycloavandulyl-lavanduquinocin] 3. In addition, oxidation of the (S)-(+)-alcohol 12 provided (S)-(+)-3, which is the enantiomer of 6-desprenyl-carquinostatin A (R)-(−)-3.
已经建立了核心咔唑结构 6-desprenyl-carquinocin 3 和 6-descycloavandulyl-lavanduquinocin 3 的不对称合成,从而实现了 carquinostatin A (1) 和 lavanduquinocin (2) 的全合成。脂肪酶 QLM (Meito) 催化外消旋醇 6 的对映选择性乙酰化,得到具有高对映选择性的 (-)-乙酸酯 7 和 (+)-醇 6。通过先进的Mosher方法,(-)-和(+)-醇6的绝对立体化学分别确定为R-和S-构型。以相同的方式,由外消旋醇12获得(-)-乙酸酯13和(+)-醇12。(R)-(-)-乙酸酯13衍生自(R)-(- )-乙酸酯7与(-)-乙酸酯13相同,已确定其为(R)-构型。 (R)-(-)-乙酸酯 13 氧化,然后水解,得到 (R)-(-)-6-去丙烯基-卡喹诺丁 [和 (R)-(-)-6-去环万杜基-薰衣喹诺辛] 3。此外,(S)-(+)-醇12的氧化提供(S)-(+)-3,其是对映体6-去戊二烯基-制卡喹他汀 A (R)-(−)-3。