title: Organocatalytic asymmetric Mannich cyclization of hydroxylactams with acetals: total syntheses of (-)-epilupinine, (-)-tashiromine, and (-)-trachelanthamidine.
abstract: An asymmetric, organocatalytic, one-pot Mannich cyclization between a hydroxylactam and acetal is described to provide fused, bicyclic alkaloids bearing a bridgehead N atom. Both aliphatic and aromatic substrates were used in this transformation to furnish chiral pyrrolizidinone, indolizidinone, and quinolizidinone derivatives in up to 89% yield and 97% ee. The total syntheses of (-)-epilupinine, (-)-tashiromine, and (-)-trachelanthamidine also achieved to demonstrate the generality of the process.
authors.affiliation: Medicinal and process Chemistry Division, CSIR-Central Drug Research Institute, Lucknow, 226031 (India). dkoley@cdri.res.in.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Koley
authors.forename: Yarkali
authors.initials: Y
authors.lastname: Krishna
authors.forename: Kyatham
authors.initials: K
authors.lastname: Srinivas
authors.forename: Afsar Ali
authors.initials: AA
authors.lastname: Khan
authors.forename: Ruchir
authors.initials: R
authors.lastname: Kant
mesh_terms: D000080:Acetals; D002384:Catalysis; D003500:Cyclization; D007212:Indolizines / Q000138:chemical synthesis*; D015394:Molecular Structure; D011763:Pyrrolizidine Alkaloids / Q000138:chemical synthesis*; D013034:Sparteine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D013237:Stereoisomerism; D000093843:Quinolizidine Alkaloids
chemical_list: D000080:Acetals; D007212:Indolizines; D011763:Pyrrolizidine Alkaloids; D013034:Sparteine; C512155:tashiromine; C015971:lupinine; D000093843:Quinolizidine Alkaloids; C051741:trachelanthamidine
keywords: acetals; alkaloids; cyclization; natural products; organocatalysis