Quesnoin, a Novel Pentacyclic ent-Diterpene from 55 Million Years Old Oise Amber

Abstract

Amber, fossilized tree resin, found at the Oise River area of the Paris basin (France) was dated as being 55 million years old. Quesnoin, a novel unique pure organic compound, was isolated from Oise amber. 1H and 13C NMR spectroscopic analysis indicated an unknown diterpene skeleton, quesnane. The absolute configurations of the eight chiral centers of quesnoin were determined to be 4S, 5S, 8R, 9S, 10S, 13S, 14R, and 16S by chiral auxiliary (R)- and (S)-phenylglycine methyl ester derivatization. Quesnoin allowed us to disclose the tree producer, corresponding to modern Hymenaea oblongifolia, Fabaceae, a subfamily of Caesalpiniaceae, one of the oldest angiosperm. The presence of the Amazon rainforest tree, H. oblongifolia, indicated that the climate of the Paris basin might have been tropical in the early Eocene period, 55 million years ago.

Chemical Characterization and Botanical Origin of French Ambers

“…10,11,42 Hymenaea was already suggested as a possible plant source for Oise amber using 1 H and 13 C NMR spectroscopic analysis, 40 although the wood associated with amber suggests another plant close to the extant genus Daniellia in the Fabaceae. 44 Solid-State CPMAS 13 C NMR Spectroscopy.…”

Abraracourcix curvivenatusn. gen. n. sp. from the Lowermost Eocene Oise amber (Hemiptera: Fulgoromorpha: Ricaniidae)

“…Th ese data interpolated, indicate the existence of fl uvio-lacustrine palaeoenvironment, i.e. a wet river forest, surrounded by semi-deciduous or deciduous woodland, which was more aff ected by dry periods, under the warm and wet seasonal climate (Nel et al 1999, Jossang et al 2008. Presence of such habitat in France support the Boreotropical hypothesis of the diversifi cation of Fabales (Doyle & Luckow 2003).…”

“…Aulacoxylon sparnacense Combes 1907, believed to be a key species of the forests of Paris Basin in Lowermost Eocene was proposed (De Franceschi & De Ploëg 2003). Th e tree fossil might correspond also to the modern genus Daniellia Bennett 1854, while chemical molecular work indicated rather the relationships with genus Hymenaea L. 1753 (Jossang et al 2008). Most of East African copal is produced by the plant Hymenea verrucosa (Gaertner 1791) also belonging to Detariae.…”

“…Th e tree supposed to produce this amber was Aulacoxylon sparnacense Combes 1907 of the order Fabales and family Caesalpiniaceae, tribe Detariae, believed to be a key species of the forests of Paris Basin in Lowermost Eocene (De Franceschi & De Ploëg 2003). However, the microscopic analysis suggested that the tree fossil might correspond to the modern genus Daniellia Bennett 1854, (Caesalpiniaceae), while chemical molecular work indicated rather the Caesalpiniaceae genus Hymenaea L. 1753 (Jossang et al 2008).…”

“…Th e amber was produced by an angiosperm, unlike the Baltic amber of gymnosperm affi nities (Feugueur 1963;Nel et al 1999, Jossang et al 2008. Th e tree supposed to produce this amber was Aulacoxylon sparnacense Combes 1907 of the order Fabales and family Caesalpiniaceae, tribe Detariae, believed to be a key species of the forests of Paris Basin in Lowermost Eocene (De Franceschi & De Ploëg 2003).…”