Three novel pentacyclic triterpenoid dienolides, phyllenolide A ( 3b-acetoxyglutina-5(10), 6-dien-27,8aolide; 1), phyllenolide B ( 3b-(benzoyloxy)glutina-5(10),6-dien-27,8a-olide; 2), and phyllenolide C ( 3b-(2hydroxybenzoyloxy)glutina-5(10),6-dien-27,8a-olide; 3), were isolated from the aerial parts of Phyllanthus myrtifolius Moon. (Euphorbiaceae). These three compounds possess an endocyclic g-lactone moiety across ring C and a homo-annular diene system in ring B. Their structures were established by analyses of CD, NOED, and 2D-NMR spectra.
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Introduction. ± The plants of the genus Phyllanthus (Euphorbiaceae) have been popularly employed for the treatment of kidney and bladder calculi, diabetes, hepatitis, and dysentery, and have also been used against affections of the intestines [1] [2]. Phyllanthus myrtifolius Moon. (Euphorbiaceae) is a small garden shrub indigenous to India and Srilanka [3]. Our earlier chemical investigation of this plant was focused on the lignans and has led to the isolation of ten new compounds of such a skeleton, i.e., phyllamyricins A ± F, retrojusticidin B and phyllamyricosides A ± C [4] [5]. Of these, retrojusticidin B and phyllamyricin B were found to possess high selectivity toward the HIV-1 reverse transcriptase [6]. Continuing our efforts in systematic phytochemical investigation of this plant, three novel pentacyclic triterpenes 1 ± 3 of glutinane type were isolated from its aerial parts. In this paper, we describe the isolation and structure elucidation of these three novel compounds.
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Results and Discussion. ± Compound 1 has a molecular formula C 32 H 46 O 4 , as deduced from its HR-FAB-MS. It contains an AcO group, as exemplified by the NMR data, d(H) 2.04 (MeCO) and d(C) at 170.8 (MeCO) and 21.2 (MeCO). Its 1 H-NMR spectrum exhibited seven additional Me singlets, an AX system for two cis-coupled olefinic H-atoms (6.35 (d) and 5.84 (d, J 9.9), and an J 3.3, 11.3, H a ÀC(3)). Its 13 C-NMR and DEPT spectra indicated the presence of a lactone C-atom (180.8 (s)), two quaternary C-atoms (139.5 and 131.1), two tertiary olefinic C-atoms (131.9 and 119.0), and an oxygenated quaternary C-atom (90.2). These data suggest that 1 contains a g-lactone moiety and a homodiene chromophore, the latter being supported by its UV absorption maximum at 269 nm (calc. 273 nm) [7]. An HMBC spectrum revealed the correlations of two Me singlets at 1.02 (Me( 23)) and 1.03 (Me( 24)) to a quaternary olefinic C-atom at 131.9 (C(5)), the carbinoyl C-atom at 79.0 (C(3)), and a quaternary aliphatic C-atom at 36.48 (C(4)), indicating that the homodiene moiety to be located at ring B. This spectrum also ( 0.15), 345 (0), 335 (À 0.