Alloprenols: novel α-trans-polyprenols of Allophylus caudatus

A novel type of polyprenols, alloprenols, with an α-trans-isoprenoid unit was found in the leaves of Allophylus caudatus (Sapindaceae) besides typical α-cis-polyprenols. The polyprenol family (Prenol-11–13, Prenol-12 dominating) was accompanied by traces of dolichols of the same chain-length. Prenol α-cis- and α-trans-isomers were chromatographically separated and their structure was analyzed by HPLC/ESI-MS, HR-ESI-MS and 1H and 13C NMR spectroscopy. Model compounds, semi-synthetic α-isomers of all-trans-Pren-9 and mainly-cis-Pren-11, were obtained using an oxidation–reduction procedure. Comparison of their NMR spectra confirmed the structure of the newly identified polyprenols. The observed pattern of NMR signal shifts may be applied for elucidation of isoprenoid structure.