Fig. 2
Isolation, characterisation and chemical structure of 25,28-bisnorgammacerane (BNG). a Total ion gas chromatography (GC)-mass spectrometry chromatograms (TIC, m/z 50–550) showing the stepwise isolation of BNG (orange diamonds): (I) the initial saturated hydrocarbon fraction, (II) the remaining fraction containing BNG after molecular sieving and preparative liquid chromatography, and (III) the isolated fraction after preparative gas chromatography containing BNG at >99% purity. b Mass spectrum (electron impact: 70 eV) of BNG (C28H48, m/z 384). c Co-elution experiment by tandem mass spectrometry (m/z 384 → 177), using a GC-tandem mass spectrometry system equipped with a DB-1-MS column, of an oil sample (top) and a sample containing abundant BNG (Te.S 20; see Fig. 1 for identification), verifying the presence of BNG in the oil (bottom). d Chemical structure of BNG (5α(H),8β,9α(H),10β(H),13β(H),14α,17β(H),18α(H)); red numbers indicate positions 25 and 28 determined based on 1H-1H correlated spectroscopy (bold), heteronuclear multiple-bond correlation (H → C) and nuclear Overhauser effect spectroscopy (also see Supplementary Methods)
