Topological selectivity in the intramolecular [4 + 1] pyrroline annulation. Formal total stereospecific synthesis of (.+-.)-supinidine, (.+-.)-isoretronecanol, and (.+-.)-trachelanthamidine

An Efficient, Overall [4+1] Cycloadditon of 1,3‐Dienes and Nitrene Precursors

“…For example, olefine dihydroxylation can lead to stereoselective synthesis of 3,4-dihydroxypyrrolidines, [7] which are core structures in many bioactive compounds. [8] Formal intramolecular [4+1] cycloadditions have been extensively studied by Hudlicky [9] and Pearson [10] via thermolysis of 1,3-dienyl azides, which proceeds via triazoline intermediates. [11] However, these reactions are often accompanied by side reactions and low yields of the [4+1] cycloadducts.…”

The Synthesis of Two Furan‐Based Analogues of the α′,β′‐Epoxy Ketone Proteasome Inhibitor Eponemycin

“…[11] The two isooctanoic acid components required for the synthesis of furan analogues 4 and 5 were prepared in a straightforward fashion by reaction of the phosphonate 8 [obtained from ethyl 4-bromocrotonate (7)] with isobutyraldehyde under HornerϪEmmons conditions. [12,13] This was followed either by (i) direct hydrolysis of the dienoate intermediate 9 (only the trans isomer was obtained) to the acid 10, or (ii) double bond reduction by catalytic hydrogenation prior to ester saponification, to give 11. Both compounds 10 and 11 were coupled with H-Ser-OMe using DCC, and the derived serine derivatives were treated with LiOH/H 2 O 2 to give the two ''left side''components 12 and 13 in high yield and high enantiomeric purity.…”

Von der Entdeckung bis zur Anwendung: 50 Jahre Vinylcyclopropan‐Cyclopenten‐Umlagerung und ihre Bedeutung in der Naturstoffsynthese

“…[39] und Retigeransäure nutzten. [40] Auf analoge Weise wurden die [4+1]-und die [3+2]-Anellierungen zu allgemeinen Methoden für die Synthese von Pyrrolizidinalkaloiden [41] und Terpenen mit Tetrahydrofuraneinheit, z. B. Ipomeamaron, [42] entwickelt.…”