作者:Marek Majewski、Ryszard Lazny
DOI:10.1021/jo00123a018
日期:1995.9
Enantioselective deprotonation of tropinone 2 with chiral lithium amides 5a and 6a, in the presence of LiCl, gave tropinone lithium enolate in up to 95% ee. The C-2 symmetrical lithium amide 6a worked best when it was generated in situ from the hydrochloride salt of the corresponding amine 6b. The deprotonation was used as the key step in synthesis of tropane alkaloids: ent-anhydroecgonine, ent-knightinol, KD-B, chalcostrobamine, ent-isobellendine, and ent-darlingine. The absolute configuration of natural benzyltropane and pyranotropane alkaloids was established (by correlation with anhydroecgonine) to be 'cocaine-like' i.e., the side chain originates at C-2 of the tropane ring system in all cases.