title: Chlorophyll Catabolites in Fall Leaves of the Wych Elm Tree Present a Novel Glycosylation Motif.
abstract: Fall leaves of the common wych elm tree (Ulmus glabra) were studied with respect to chlorophyll catabolites. Over a dozen colorless, non-fluorescent chlorophyll catabolites (NCCs) and several yellow chlorophyll catabolites (YCCs) were identified tentatively. Three NCC fractions were isolated and their structures were characterized by spectroscopic means. Two of these, Ug-NCC-27 and Ug-NCC-43, carried a glucopyranosyl appendage. Ug-NCC-53, the least polar of these NCCs, was identified as the formal product of an intramolecular esterification of the propionate and primary glucopyranosyl hydroxyl groups of Ug-NCC-43. Thus, the glucopyranose moiety and three of the pyrrole units of Ug-NCC-53 span a 20-membered ring, installing a bicyclo[17.3.1]glycoside moiety. This structural motif is unprecedented in heterocyclic natural products, according to a thorough literature search. The remarkable, three-dimensional bicyclo[17.3.1]glycoside architecture reduces the flexibility of the linear tetrapyrrole. This feature of Ug-NCC-53 is intriguing, considering the diverse biological effects of known bicyclo[n.3.1]glycosidic natural products.
authors.affiliation: Institute of Organic Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria.
authors.forename: Mathias
authors.initials: M
authors.lastname: Scherl
authors.affiliation: Institute of Organic Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.affiliation: Institute of Organic Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria.
authors.forename: Christoph R
authors.initials: CR
authors.lastname: Kreutz
authors.affiliation: Institute of General, Inorganic & Theoretical Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria.|Bioinformatics Institute, Agency for Science, Technology & Research, 30 Biopolis Street, 138671, Singapore, Singapore.
authors.forename: Roland G
authors.initials: RG
authors.lastname: Huber
authors.affiliation: Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland. zass@retired.ethz.ch.
authors.forename: Engelbert
authors.initials: E
authors.lastname: Zass
authors.affiliation: Institute of General, Inorganic & Theoretical Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria. Klaus.Liedl@uibk.ac.at.
authors.forename: Klaus R
authors.initials: KR
authors.lastname: Liedl
authors.affiliation: Institute of Organic Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria. bernhard.kraeutler@uibk.ac.at.
authors.forename: Bernhard
authors.identifier: http://orcid.org/0000-0002-2222-0587
authors.initials: B
authors.lastname: Kräutler
mesh_terms: D002734:Chlorophyll / Q000737:chemistry*; D003116:Color; D005456:Fluorescent Dyes / Q000737:chemistry*; D006031:Glycosylation; D018515:Plant Leaves / Q000737:chemistry*; D013057:Spectrum Analysis; D034403:Ulmus / Q000737:chemistry* / Q000502:physiology
chemical_list: D005456:Fluorescent Dyes; D002734:Chlorophyll
keywords: chlorophyll; glycoside; natural products; plant senescence; tetrapyrrole