Old problems, new ideas! The biomimetic phenol coupling of norbelladine derivatives such as 1 (Bn = benzyl) to form galanthamine (2), a drug used in the treatment of Alzheimer's disease, has been greatly improved by the use of the hypervalent-iodine oxidation reagent phenyliodine(III) bis(trifluoroacetate) (PIFA).
employing a novel remote asymmetric induction, where conformation of the seven-memberedring in the product of the phenol coupling was restricted by forming a fused-chiral imidazolidinone ring with D-phenylalanine on the benzylic C-N bond of the tri-O-alkylated gallyl amino moiety. The conformational restriction and successive debenzylation of the protected hydroxyl groups on the pyrogallol ring caused
A New H<sub>2</sub>O<sub>2</sub>/Acid Anhydride System for the Iodoarene-Catalyzed C−C Bond-Forming Reactions of Phenols
作者:Toshifumi Dohi、Yutaka Minamitsuji、Akinobu Maruyama、Satoshi Hirose、Yasuyuki Kita
DOI:10.1021/ol801321f
日期:2008.8.21
We have succeeded in the first versatile iodoarene-catalyzed C-C bond-forming reactions by development of a new reoxidation system at low temperatures using stoichiometric bis(trifluoroacetyl) peroxide A in 2,2,2-trifluoroethanol (TFE). The catalytic system supplies a wide range of substrates and functional availabilities sufficient to be used in the key synthetic process of producing biologically important Amaryllidaceae alkaloids.