Synthesis of Diels–Alder adducts of the quinolizidine alkaloids N-methylcytisine, (−)-leontidine, and (−)-thermopsine with N-phenylmaleimide

The Diels–Alder adducts of the quinolizidine alkaloids N-methylcytisine, (−)-leontidine, and (−)-thermopsine with N-phenylmaleimide have been synthesized. The structures and absolute configurations of the new asymmetric centers of the products were determined by NMR spectroscopy experiments, QC-calculations, and X-ray data.

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(3aS,4R,8S,12R,12aR,12bS)-10-Methyl-2-phenylocta-hydro-1H-4,12a-etheno-8,12-methanopyrrolo[3′,4′:3,4]pyrido[1,2-a][1,5]diazocine-1,3,5(4H)-trioneC22H23N3O3[α]D20=+41.2 (c 0.9, CHCl3)Source of chirality: (−)-cytisineAbsolute configuration: (3aS,4R,8S,12R,12aR,12bS)

(3aR,4S,8S,12R,12aS,12bR)-10-Methyl-2-phenylocta-hydro-1H-4,12a-etheno-8,12-methanopyrrolo[3′,4′:3,4]pyrido[1,2-a][1,5]diazocine-1,3,5(4H)-trioneC22H23N3O3[α]D20=-5.2 (c 1.1 CHCl3)Source of chirality: (−)-cytisineAbsolute configuration: (3aR,4S,8S,12R,12aS,12bR)

(3aS,4R,8S,8aS,14S,14aR,14bS)-2-Phenyldecahydro-1H-4,14a-etheno-8,14-methanopyrrolo[1,2-a]pyrrolo[3′,4′:3,4]pyrido[1,2-e][1,5]diazocine-1,3,5(4H)-trioneC24H25N3O3[α]D20=+5.0 (c 1.0 CHCl3)Source of chirality: (−)-leontidineAbsolute configuration: (3aS,4R,8S,8aS,14S,14aR,14bS)

(3aR,4S,8S,8aS,14S,14aS,14bR)-2-Phenyldecahydro-1H-4,14a-etheno-8,14-methanopyrrolo[1,2-a]pyrrolo[3′,4′:3,4]pyrido[1,2-e][1,5]diazocine-1,3,5(4H)-trioneC24H25N3O3[α]D20=-12.2 (c 1.3 CHCl3)Source of chirality: (−)-leontidineAbsolute configuration: (3aR,4S,8S,8aS,14S,14aS,14bR)

(3aS,4R,8S,8aR,15S,15aR,15bS)-2-Phenyldeca-hydro-1H,7H-4,15a-etheno-8,15-methanopyrido[1,2-a]pyrrolo[3′,4′:3,4]pyrido[1,2-e][1,5]diazocine-1,3,5(4H)-trioneC25H27N3O3[α]D20=+32.4 (c 1.1, CHCl3)Source of chirality: (−)-thermopsineAbsolute configuration: (3aS,4R,8S,8aR,15S,15aR,15bS)

(3aR,4S,8S,8aR,15S,15aS,15bR)-2-Phenyldeca-hydro-1H,7H-4,15a-etheno-8,15-methanopyrido[1,2-a]pyrrolo [3′,4′:3,4]pyrido[1,2-e][1,5]diazocine-1,3,5(4H)-trioneC25H27N3O3[α]D20=-2.1 (c 0.8, CHCl3)Source of chirality: (−)-thermopsineAbsolute configuration: (3aR,4S,8S,8aR,15S,15aS,15bR)