Enantioselective syntheses of (+)-α-skytanthine, (+)-δ-skytanthine and (+)-iridomyrmecin by an intramolecular magnesium-ene reaction.

✍ Scribed by Wolfgang Oppolzer; E.Jon Jacobsen

• Publisher: Elsevier Science
• Year: 1986
• Tongue: French
• Weight: 222 KB
• Volume: 27
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)84199-4

✦ Synopsis

Starting from (S)-3-methyl-l-penten-5-01 k enantiomerically pure (+)-a-skytanthine 2, (+)-6-skytanthine 11 and (+)-iridomyrmecin 12 were synthesized via the magnesium-ene reaction 2 + 1.

In extension of previous work on intramolecular Mg-ene reactions 2 we considered the prospect of synthesizing monoterpene alkaloids and iridoids & via the key step 2 -+ 1 (Scheme l).It was hoped that the preexisting chiral center in 2 would induce the desired configuration at the newly formed centers.

Scheme 1

We report here the application of this concept to the total syntheses of enantiomerically pure (+)-a-skytanthine 9, 3 (+)-6-skytanthine II 3 and (+)-iridomyrmecin 12 1 (Scheme 2).