RING-A FISSIONED 3,4-SECO-3-NOR-TRITERPENE-2-ALDEHYDES AND RELATED PENTACYCLIC TRITERPENOIDS FROM THE LEAF WAX OF HOYA-AUSTRALIS

The leaf wax of Hoya australis has been shown to contain a series of new 3,4-seco-3-nor-triterpene-2-aldehydes (proposed names australinals A-D), the related 3,4-seco-3-nor-2-ol derivatives (australinols A-D) and their precursors, the non-fissioned pentacyclic triterpenols delta-amyrin, beta-amyrin, lupeol and alpha-amyrin. Minor amounts of psi-taraxasterol and taraxasterol-derived compounds were also present (australinals E and F, and australinols E and F) as well as traces of methylated 3,4-seco-3-acid derivatives of beta- and delta-amyrin (methyl dihydronyctanthate and methyl dihydroaustralinoate. From the present data, it follows that the structures of the seco-nor-triterpenols, of which australinol B was published before as the 1-ol derivative, must be revised to a 2-ol derivative. To our knowledge, compounds australinals A-F, australinols A, C-F and methyldihydroaustralinoate have not been described from living plants before.