Ammonium quinolizidines

The nitrogen atom in quinolizidine derivatives behaves as a tertiary amine and hence it can undergo quaternization by reaction with alkyl halides. For instance, berberine derivative 101 was transformed into 102 by treatment with 3-iodopropanol followed by anion exchange. Compound 102 was then transformed into intermediate 103, which was employed as a precursor for the the preparation of bis-ammonium salt 104 (Scheme 10). This compound showed ultrashort curare-like activity in rhesus monkeys <2001JOC3495>. 

The cyclic ammonium ylide/[l,2]-shift approach has been successfully applied by West and Naidu to a key step in the total synthesis of (—)-epilupinine, one of the biologically active lupin alkaloids. Cu(acac)2-catalyzed diazo decomposition of enantiomeric pure diazoketone 160 in refluxing toluene generates a spiro ammonium ylide 161 and 162, which then undergoes [l,2]-shift to give rise to a quinolizidine skeleton as a mixture of diastereomers (95 5) (Scheme Major diastereomer 164 has enantiomeric purity of 75% ee. The partial retention of stereo-... 

In the laboratory of F.G. West, the stereoselective silyl-directed [1,2]-Stevens rearrangement of ammonium ylides was investigated as a potential key step toward the enantioselective synthesis of various hydroxylated quinolizidines. The dimethylphenylsilyl group served as a surrogate for one of the hydroxyl groups in the product. The Fleming-Tamao oxidation was performed under Denmark s conditions to avoid oxidation of the tertiary amine to the corresponding A/-oxide, and the desired quinolizidine did was obtained in 81% yield. 

Quantitative analysis of quinolizidine alkaloids in Chinese herbs 1% acetic acid, 50 mM ammonium acetate, 20% acetonitrile in methanol NACE [185]... 

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