title: Nigramides A-S, dimeric amide alkaloids from the roots of Piper nigrum.
abstract: [structure: see text] Fifteen novel dimeric amide alkaloids possessing a cyclohexene ring, nigramides A-O (1-15), as well as four novel dimeric amide alkaloids possessing a cyclobutane ring, nigramides P-S (17-20), have been isolated from the roots of Piper nigrum. Their structures were elucidated on the basis of their spectroscopic data. The biosynthestic hypothesis of nigramides A-O (1-15) was proposed by an intermolecular Diels-Alder reaction from the corresponding monomeric amides. On the basis of this biosynthetic hypothesis, the first study of the thermal and Lewis acid mediated Diels-Alder reactions of piperine in different organic solvents and under solventless conditions is also described.
authors.affiliation: Faculty of Pharmaceutical Sciences, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan.
authors.forename: Kun
authors.initials: K
authors.lastname: Wei
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Kazuo
authors.initials: K
authors.lastname: Koike
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Chen
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Nikaido
mesh_terms: D000470:Alkaloids / Q000737:chemistry* / Q000302:isolation & purification*; D000577:Amides / Q000737:chemistry*; D052117:Benzodioxoles; D002384:Catalysis; D018360:Crystallography, X-Ray; D003500:Cyclization; D003510:Cyclohexanes / Q000737:chemistry; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008968:Molecular Conformation; D015394:Molecular Structure; D029222:Piper nigrum / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry*; D053284:Polyunsaturated Alkamides; D012997:Solvents; D013696:Temperature
chemical_list: D000470:Alkaloids; D000577:Amides; D052117:Benzodioxoles; D003510:Cyclohexanes; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D012997:Solvents; C008922:piperine