Enantioselective Synthesis of cis- and trans-2-Methyl-6-nonylpiperidines: Alkaloids Solenopsin and Isosolenopsin
摘要:
The cross-metathesis of the enantioenriched homoallylic amine 8 (readily accessible by alpha-aminoallylation of decanal) with methyl vinyl ketone using the Hoveyda-Blechert catalyst 10 in presence of 10 mol% of Ti(O-i-Pr)(4) led exclusively to the (E)-enone 11, which by stereoselective reductive amination affords (+)-isosolenopsin (3a) and (+)-solenopsin (4a) with excellent selectivities.
Synthesis of (+)-solenopsin, a 2,6-disubstituted piperidine alkaloid, isolated from fire ants (Solenopsis), was achieved. Stereoselective construction of trans-2,6-piperidine ring moiety was performed using palladium-catalyzed cyclization. Chain elongation using Grubbs 2nd catalyst followed by the reduction of doublebond and the deprotection of the Cbz group afforded (+)-solenopsin.