ISOLATION AND STRUCTURE DETERMINATION OF 3 TRITERPENES FROM BARK RESIN OF JUVENILE EUROPEAN WHITE BIRCH

2beta-O-acetyl-25-hydroxy-(20S,24R)-epoxydammarane (papyriferic acid) and two previously unknown dammarane triterpenes were identified from diethylether extracts of bark resin from juvenile Betula pendula. H-1 and C-13 NMR spectroscopy showed that a compound appearing often in ch romatographic analyses in amounts comparable with papyriferic acid is its 3beta-epimer. The third compound which is abundant in individuals with low levels of the other two compounds was shown to be malonyl-12b eta-O-acetyl-20(S)-hydroxydammar-24-ene (pendulic acid), i.e. an analo gue of the 3beta-epimer of papyriferic acid with open and partially re duced C-17 side chain.