Claude Hootele

Asymmetric nitrone-vinyl sulfoxide cycloadditions

Abstract The cycloaddition of (Z) and (E)-vinyl sulfoxides with cyclic nitrones 1 and 2 is reported. Best diastereoselection is achieved with (Z)-vinyl sulfoxides 7a-d as dipolarophiles. This methodology allows the highly stereoselective synthesis of (+)-sedridine 9a , (−)-hygroline 10 and (−)-(2S)-N-carbomethoxypelletierine 11a .

Myrtine and epimyrtine, quinolizidine alkaloids from vaccinium myrtillus

Abstract The structures (including conformation and absolute configuration) of myrtine and epimyrtine, quinolizidine alkaloids from Vaccinium myrtillus, are reported. The two bases are obtainable from pelletierine by Mannich condensation with acetaldehyde, or can be derived stereospecifically by 1,4-nucleophilic addition to enaminones. They have been resolved with tartaric acid. The isomerization of myrtine is discussed.

Hydroboration of enecarbamates and the synthesis of β-hydroxypiperidine alkaloids

The β-hydroxypiperidine alkaloids 5, 6 and 8 were diastereoselectively synthesized using hydroboration of enecarbamates 2b-c as a key step.

Asymmetric nitrone-vinyl sulfoxide cycloadditions: A highly enantioselective synthesis of (+)-sedridine

Abstract Cycloaddition of 2,3,4,5-tetrahydropyridine-1-oxide 1 to ( Z )-( R )-vinyl sulfoxides 2 a-d proceeds in high yield to give isoxazolidines 3 a-d and 4 a-d with complete exo selectivity and with 82–98% asymmetric induction. This method provides an efficient synthesis of the enantiomerically pure piperidine alkaloid (+)-sedridine 6 a .

Sedum alkaloids. X. Structure and synthesis of new 3- and 5-hydroxypiperidine alkaloids

Abstract The structure and absolute configuration of (-)-3-hydroxynorallosedamine 1 , (-)-3-hydroxyallosedamine 2 and (-)-5-hydroxysedamine 3 , three new minor alkaloids isolated from Sedum acre , are reported. A nitrone-based synthesis of the new bases is described.

Distribution des alcaloides dans le genre Lycopodium

Abstract The alkaloid content of Lycopodium saururus , L. carolinianum , L. cernuum , L. clavatum , L. issleri , L. sitchense , L. carolinum , L. contiguum and L. thyoides has been investigated. The results obtained and the distribution of the alkaloids in the genus are discussed from a chemotaxonomic point of view.

Myricoidine and dihydromyricoidine, two new macrocyclic spermidine alkaloids from clerodendrum myricoides

Abstract Two new spermidine alkaloids, myricoidine 1 and dihydromyricoidine 2 have been isolated from Clerodendrum myricoides (Verbenaceae) and their structures established by a study of their spectral and chemical properties.

Sedum alkaloids. VIII. solution conformation of sedamine and related bases

Abstract The preferred solution conformation of sedamine, allosedamine, norsedamine and norallosedamine was established by high resolution proton and carbon-13 NMR spectroscopy.

A new efficient synthesis of β-aminoketones via Δ4-isoxazolines.

Abstract β-aminoketones are prepared in good yield by hydrogenolysis (Pd/C) of the NO bond of Δ 4 -isoxazolines obtained by 1,3-dipolar cycloaddition of nitrones with alkynes.

Sedum alkaloids. VII: Structure and synthesis of (+)-4-hydroxysedamine and (±)-4-hydroxyallosedamine

Abstract The structures of (+)-4-hydroxysedamine 1 and (+)-4-H-hydroxyallosedamine 2, two new minor alkaloids from Sedum itacre, are reported 1 and 2 were synthesized, and their absolute configuration established, via the optically pure tetrahydro 1,3-oxazines 17 and 18.