A concise enantioselective synthesis of (+)-lentiginosine

A high yielding enantioselective synthesis of the indolizidine alkaloid, (+)-lentiginosine, has been described based on asymmetric aza-Cope rearrangement and the l-proline catalyzed α-aminooxylation of aldehydes. The strategy also makes use of ring-closing metathesis for the construction of piperidine core.

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(S)-1-(Benzyloxy)pent-4-en-2-amineC12H17NO[α]D25=+7.2 (c 1.4, CHCl3)Source of chirality: asymmetric aza-Cope rearrangementAbsolute configuration: (S)

tert-Butyl (S)-1-(benzyloxy)pent-4-en-2-ylcarbamateC17H25NO3[α]D25=-5.8 (c 0.86, CHCl3)Source of chirality: asymmetric aza-Cope rearrangementAbsolute configuration: (S)

tert-Butyl allyl-(S)-1-(benzyloxy)pent-4-en-2-ylcarbamateC20H29NO3[α]D25=+2.05 (c 1.46, CHCl3)Source of chirality: asymmetric aza-Cope rearrangementAbsolute configuration: (S)

(S)-tert-Butyl 6-((benzyloxy)methyl)-5,6-dihydropyridine-1(2H)-carboxylateC18H25NO3[α]D25=+20 (c 1, CHCl3)Source of chirality: asymmetric aza-Cope rearrangementAbsolute configuration: (S)

(S)-tert-Butyl 2-(hydroxymethyl)piperidine-1-carboxylateC11H21NO3[α]D25=-40.1 (c 1, CHCl3)Source of chirality: asymmetric aza-Cope rearrangementAbsolute configuration: (S)

(S)-tert-Butyl 2-((E)-2-(ethoxycarbonyl)vinyl)piperidine-1-carboxylateC15H25NO3[α]D25=-77.5 (c 1.3, CHCl3)Source of chirality: asymmetric aza-Cope rearrangementAbsolute configuration: (S)