合成路线1

18) Ring contraction of the tropinone skeleton via a Favorskii rearrangement. Bai et al. utilized the readily available tropinone (LXXIII) as a starting material. Compound (LXXIV), which could be obtained from (LXXIII) in one step, was brominated with cupric bromide to give the monobromide (LXXV). Without separation of the two isomers, both isomers (LXXV) underwent Favorskii rearrangement to yield the expected ester (LXXVI). The key intermediate (LXXVII) was then obtained by selenation of (LXXVI) followed by selenoxide elimination. A palladium-catalyzed Heck-type coupling of (LXXVII) and 2-chloro-5-iodopyridine (LVII) furnished the exo-isomer (LXXVIII) stereoselectively in 56% yield. Conversion of (LXXVIII) to (I) was achieved by radical decarboxylation of the corresponding thiohydroxamic ester followed by cleavage of the carbamate with iodotrimethyl silane.