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Structure Determination of Tigridial, an Iridopentaene from Tigridia pavonia (Iridaceae)
Author(s) -
Effers Kerstin,
Scholz Bettina,
Nickel Christoph,
Hanisch Bernadette,
Marner FranzJosef
Publication year - 1999
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199911)1999:11<2793::aid-ejoc2793>3.0.co;2-z
Subject(s) - chemistry , stereochemistry , moiety , natural product , hemiacetal , hydroquinone , conjugated system , iridaceae , two dimensional nuclear magnetic resonance spectroscopy , nuclear magnetic resonance spectroscopy , bicyclic molecule , organic chemistry , botany , biology , polymer
Besides numerous known iridals, which are unusual mono‐ or bicyclic triterpenoids of Iridaceae, lipid extracts of Tigridia pavonia bulbs contain tigridial ( 17 ), a new spirobicyclic hemiacetal with a conjugated pentaene moiety in the terpenoid side chain. The isolated natural product decomposes rapidly despite exclusion of light and oxygen. In contrast, derivatives of 17 formed by Diels–Alder reaction with 4‐phenyl‐3 H ‐1,2,4‐triazole‐3,5‐(4 H )‐dione ( 13 ) are stable, as are the products of a subsequent reduction with NaBH 4 . The products 15a,b and 16a,b of this reaction sequence were isolated and their structures elucidated by spectroscopic techniques. From these results structure 17 was inferred for the new natural product, which was confirmed by 1D and 2D NMR spectroscopy of a mixture of 11 and 17 , in which the latter had been stabilized by addition of hydroquinone. The stereochemistry of 17 was deduced from 2D NOE experiments and comparison with known compounds.