Lipase-Catalyzed Asymmetric Synthesis of Desprenyl-carquinostatin A and Descycloavandulyl-lavanduquinocin

摘要

An asymmetric synthesis of the core carbazole structure,6-desprenyl-carquinbstatin 3 and 6-descycloavan-dulyl-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(-)-ac-etate 7 and the(+)-alcohol 6 with high enantioselectivity.The absolute stereochemistry of the(-)-and(+)-alco-hol 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-de-sprenyl-carquinostatin [and(R)-(-)-6-descycloavandulyl-lavanduquinocin] 3.In addition,oxidation of the(S)-(-1-)-alcohol 12 provided(S)-(+)-3,which is the enantiomer of 6-desprenyl-carquinostatin A(R)-(-)-3.