title: Antiherbivore prenylated benzoic acid derivatives from Piper kelleyi.
abstract: The known prenylated benzoic acid derivative 3-geranyl-4-hydroxy-5-(3″,3″-dimethylallyl)benzoic acid (1) and two new chromane natural products were isolated from the methanolic extract of the leaves of Piper kelleyi Tepe (Piperaceae), a midcanopy tropical shrub that grows in lower montane rain forests in Ecuador and Peru. Structure determination using 1D and 2D NMR analysis led to the structure of the chromene 2 and to the reassignment of the structure of cumanensic acid as 4, an isomeric chromene previously isolated from Piper gaudichaudianum. The structure and relative configuration of new chromane 3 was determined using 1D and 2D NMR spectroscopic analysis and was found to be racemic by ECD spectropolarimetry. The biological activity of 1-3 was evaluated against a lab colony of the generalist caterpillar Spodoptera exigua (Noctuidae), and low concentrations of 2 and 3 were found to significantly reduce fitness. Further consideration of the biosynthetic relationship of the three compounds led to the proposal that 1 is converted to 2 via an oxidative process, whereas 3 is produced through hetero-[4+2] dimerization of a quinone methide derived from the chromene 2.
authors.affiliation: Department of Chemistry, University of Nevada, Reno , Reno, Nevada 89557, United States.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Jeffrey
authors.forename: Michael D
authors.initials: MD
authors.lastname: Leonard
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Glassmire
authors.forename: Craig D
authors.initials: CD
authors.lastname: Dodson
authors.forename: Lora A
authors.initials: LA
authors.lastname: Richards
authors.forename: Massuo J
authors.initials: MJ
authors.lastname: Kato
authors.forename: Lee A
authors.initials: LA
authors.lastname: Dyer
mesh_terms: D001565:Benzoates / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D001578:Benzopyrans / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D004484:Ecuador; D060434:Herbivory / Q000502:physiology*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010568:Peru; D031701:Piper / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D054876:Prenylation
chemical_list: D001565:Benzoates; D001578:Benzopyrans