Yvonne Gelas-Mialhe

Asymmetric synthesis of quinolizidine alkaloids (−)-lasubine I, (−)-lasubine II and (+)-subcosine II

Abstract The enantioselective synthesis of (−)-lasubine I 1 and the first asymmetric synthesis of (−)-lasubine II 2 and (+)-subcosine II 3 is described. The key step is the intramolecular cyclization of N-acyliminium ion 4 which is derived from (S)-aminoester 6.

Enantioselective synthesis of (−)-indolizidine 167B

Abstract The enantioselective total synthesis of (−)-indolizidine 167B is described. The key step is the intramolecular cyclization of the chiral N -acyliminium ion 6 . Indolizidine 167B was obtained in 7 steps and 17% yield from ethyl ( R )-3-aminohexanoate, with an enantiomeric excess of 93%.

Diastereoselective cyclization of allylsilanes on α-acyliminium ions. A new approach to (±)-myrtine and (±)-epimyrtine

Abstract Total synthesis of (±)-myrtine and (±) epimyrtine is described using an intromolecular allylsi1ane N acyliminium ion cyclization.

ENANTIOSELECTIVE SYNTHESIS OF THE QUINOLIZIDINE ALKALOIDS (+)-MYRTINE AND (-)-EPIMYRTINE

Abstract The enantioselective synthesis of (+)-myrtine 1 and (−)-epimyrtine 2 is described starting from ( S )-2-(2-hydroxypropyl)allyltrimethylsilane 4 using an intramolecular allylsilane N -acyliminium ion cyclization.

A convenient allylsilane-N-acyliminium route toward 5-alkylindolizidines. Diastereoselective synthesis of (±)-indolizidine 167B

Abstract A highly diastereoselective synthesis of 5-alkylindolizidines is described via an intermolecular addition of the allylsilyl functional group of homoallylic alcohols with an N -acyliminium ion derived from pyrrolidin-2-one.

Enantioselective synthesis of 5-substituted pipecolic acids using an intramolecular allylsilane-iminium ion cyclization

Abstract The application of the intramolecular allylsilane-iminium ion cyclization reaction for the enantioselective synthesis of piperidine derivatives is described. The synthetic potential of this methodology is demonstrated by the enantioselective synthesis of 5-substituted pipecolic acids.

A facile enantioselective synthesis of 2-(2-aminoethyl)allylsilanes, new synthons for piperidine synthesis

Abstract The synthesis of chiral (2-substituted-2-aminoethyl)allylsilanes by cerium mediated trimethylsilylmethylmagnesium chloride addition to the ester group of non racemic chiral β-aminoesters is described.

Enantioselective synthesis of 2-(2-hydroxyethyl)allylsilanes from chiral β-hydroxyesters

Abstract The synthesis of chiral (2-substituted-2-hydroxyethyl)allylsilanes by cerium mediated trimethylsilylmethylmagnesium chloride addition on chiral β-hydroxyesters is described.

Synthetic studies on indole alkaloids. V. Synthesis of 2-methyleneindolo [2,3-a] quinolizidines

A synthesis of 2-methyleneindolo [2,3-a] quinolizidine (6) by the intramolecular cyclization of N-(2-hydroxyethyl)-2-[1-phenylsulfonyl)-3-indolyl]-4-methylenepiperidine (9) by the action of t-C 4 H 9 OK is reported

Synthetic studies on indole alkaloids VIII. 1 Synthesis and reactivity of asymmetric 2-indolyi-4-methylenepiperidines

Abstract The synthesis of asymmetric 2-indolyl-4-methylenepiperidines 8–11 and 14–15 by condensation of an aminoallylsilane with an indole carbaldehyde, followed by intramolecular cyclization of the intermediate, is described. The reactivity of N-(2-hydroxyethyl)indolylpiperidines 9 and 14 with KtBuO to give indolo[2,3-a]quinolizidines is studied. Some unexpected results are obtained due to the influence of the α-phenyl ring.