title: Total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine.
abstract: A full account of the total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine is presented. Two approaches have been developed to construct the basic pyrrolo[1,2-a]azepine core of the Stemona alkaloids, featuring a tandem semipinacol/Schmidt rearrangement of a secondary azide and a highly stereoselectively desymmetrizing intramolecular Schmidt reaction, respectively. To build the common spiro-γ-butyrolactone, a new protocol was carried out by utilizing an intramolecular ketone-ester condensation as the key transformation. The vicinal butyrolactone moiety of (±)-maistemonine was stereoselectively introduced via a one-pot procedure involving the epimerization at C-3 and carbonyl allylation/lactonization. Moreover, (±)-stemonamide was divergently synthesized from a common intermediate, and (±)-isomaistemonine was obtained via the epimerization of (±)-maistemonine at C-12.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, P. R. China.
authors.forename: Zhi-Hua
authors.initials: ZH
authors.lastname: Chen
authors.forename: Zhi-Min
authors.initials: ZM
authors.lastname: Chen
authors.forename: Yong-Qiang
authors.initials: YQ
authors.lastname: Zhang
authors.forename: Yong-Qiang
authors.initials: YQ
authors.lastname: Tu
authors.forename: Fu-Min
authors.initials: FM
authors.lastname: Zhang
mesh_terms: D015107:4-Butyrolactone / Q000737:chemistry; D000470:Alkaloids / Q000138:chemical synthesis*; D001381:Azepines / Q000138:chemical synthesis* / Q000737:chemistry; D001386:Azides / Q000737:chemistry; D001688:Biological Products / Q000138:chemical synthesis*; D053138:Cyclohexenes / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D007659:Ketones / Q000737:chemistry; D058116:Lewis Acids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013141:Spiro Compounds / Q000138:chemical synthesis*; D041901:Stemonaceae / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D001381:Azepines; D001386:Azides; D001688:Biological Products; D053138:Cyclohexenes; D004952:Esters; D007659:Ketones; D058116:Lewis Acids; D013141:Spiro Compounds; C571610:maistemonine; C519041:semipinacol; C434309:stemonamide; D015107:4-Butyrolactone