Spiro-triterpenes from clay-catalysed rearrangement of hopenes: NMR structural elucidation and occurrence in a recent sediment

Article abstract of DOI:10.1016/S0040-4039(00)76804-3

Acidic K-10 montmorillonite clay-catalysed rearrangement of hop-22(29)-ene 5 and of hop-17(21)-ene 6 leads to the formation of small quantities of various fernenes and of new compounds, the 14-methyl-13,15-cyclo-B':A'-neo-26-nor-14,15-seco-18α-gammacer-7-ene 8 and its Δ⁸- and Δ⁹((11))-isomers 9 and 10, the structures of which have been established by MS and NMR spectroscopy. This novel hopane skeleton transposition also operates on bacterial sedimentary hopenes, as shown by GC-MS investigations of the alkene fraction from a recent lacustrine sediment.