Synthesis of Tropane Alkaloids via Enantioselective Deprotonation of Tropinone
摘要:
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.
作者:Peter L. Katavic、Mark S. Butler、Ronald J. Quinn、Paul I. Forster、Gordon P. Guymer
DOI:10.1016/s0031-9422(99)00263-0
日期:1999.10
A new gamma-pyranotropane, darlingine N-oxide, was isolated from the bark and leaves of Darlingia darlingiana, along with the known compound, darlingine. 1D-NOESY NMR experiments indicated that the N-methyl groups of both alkaloids were orientated towards the pyran ring. (C) 1999 Elsevier Science Ltd. All rights reserved.