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Helvetica Chimica Acta – Vol. 89 (2006)
with a XTI-5 (bonded, 5% phenyl) capillary column (30 m×0.32 mm; film thickness 0.25 mm) and cou-
pled to a Shimadzu 2010 mass selective detector; oven temp. was programmed from 608 at 58/min; He as
carrier gas at a flow rate of 1.8 ml/min; ion-source temp. 2008, interface temp. 2208, solvent cut time 2
min, and detector voltage 1 kV; scanning from m/z 60 to 400 for 85 min; PCI mode for analysis with iso-
butane as the reagent gas.
2. Purification of Elemol (1). The higher boiling fraction of Java citronella oil (supplied by Nishant
Aromas, Mumbai) was subjected to CC (SiO2, gradient petroleum ether/AcOEt). The fraction eluted
with petroleum ether/AcOEt 95 :5 furnished 1. Colorless crystals (MeOH). M.p. 528 ([1]: 538). Rf
(AcOEt/light petroleum ether 8 :92) 0.5. [a]D =À4.73 (c=2.3, CHCl3).
3. Dehydration of Elemol (1). To a soln. of 1 (3.5 g) in AcOH (42 ml), 60% perchloric acid (0.7 ml)
was added dropwise, and the mixture was left at 25–278 for 72 h with stirring. The dark brown soln. was
diluted with H2O and extracted with Et2O, the Et2O layer washed free from acid, dried, and evaporated,
and the residue subjected to careful CC (silica gel). Besides a-elemene (4) and d-elemene (5), 0.28 g (8%)
of 2 was obtained (with AcOEt/light petroleum ether 4 :96) and 0.12 g (3.4%) of 3 (with AcOEt/light
petroleum ether 5 :95; after purification by repeated CC (silica gel)).
Data of Elemoxide (=(3S,4aR,7aR)-1,3,3a,4,7,7a-hexahydro-6-isopropyl-1,1,3,3a-tetramethylisoben-
zofuran; 2): Rf (AcOEt/light petroleum ether 4 :96) 0.6. [a]D =À57.2 (c=1.1, EtOH). IR (KBr): 2964,
1640, 1377, 1365, 1184, 1068, 950, 808, 777. 1H- and 13C-NMR: Table. EI-MS: 222(14.4), 207(30.2),
178(14.4), 163(32.4), 149(10.8), 135(74.8), 121(46), 107(44), 93(100), 79(18), 43(43).
Data of (+)-b-Cyperone (=(4aS)-4,4a,5,6-Tetrahydro-7-isopropyl-1,4a-dimethylnaphthalen-2(3H)-
one; 3): Rf (AcOEt/light-petroleum ether 6 :94) 0.4. [a]D =+365 (c=1.5, CHCl3). IR (neat): 2925,
1658, 1618, 1323, 1288. 1H-NMR: 6.29 (d, J=2.1, HÀC(8)); 2.7–2.1 (m, CH2(3), CH2(6), Me2CH);
1.87 (br. s, MeÀC(1)); 1.78–1.5 (m, 4 H); 1.11 (s, MeÀC(4a)); 1.084 (d, J=2.1, Me2CH). 13C-NMR:
199.2 (s, C(2)); 156.2 (s, C(1)); 156.0 (s, C(8a)); 126.35 (s, C(7)); 118.2 (d, C(8)); 37.1 (t, C(4)); 36.4 (t,
C(5)); 36.1 (d, Me2CH); 33.8 (t, C(3)); 33.2 (s, C(4a)); 23.7 (t, C(6)); 21.5 (q, MeCHMe); 21.0 (q,
MeCHMe, MeÀC(4a)); 10.1 (q, MeÀC(1)). EI-MS: 218 (25, M+), 203 (43), 175 (47), 147 (21), 119
(32), 91 (100).
5. 2,4-Dinitrophenylhydrazone of 3. To a soln. of 2,4-nitrophenylhydrazine (50 mg) in MeOH (5 ml),
3 drops of conc. HCl soln. were added, followed by 3 (120 mg) in MeOH. The mixture was allowed to
stand for a few minutes. Then, the formed red precipitate was filtered and purified by CC (silica gel,
AcOEt/light petroleum ether 1:9): bright red needles. M.p. 216–2188 ([13]: 2188). [a]D =+721
(c=0.6, CHCl3). Rf (AcOEt/light petroleum ether 1:9) 0.6. IR (KBr): 3311, 2927, 1618, 1591, 1500,
1
1336, 1309. H-NMR: 11.3 (s, 1 H); 9.13 (d, J=3, 1 H); 8.05 (d, J=7.5, 1 H); 8.3 (dd, J=7.5, 3, 1 H);
6.4 (s, 1 H); 1.0 (s, 3 H); 1.118 (d, J=6.9, 6 H); 2.08 (s, 3 H). 13C-NMR: 155.8 (s); 144.7 (s); 147.8 (s);
152.2 (s); 129.9 (d); 129.5 (s); 123.6 (d); 117.9 (d); 32.7 (s); 23.5 (t); 21.6 (t); 21.6 (q); 21.2 (q). EI-MS:
398 (100, M+), 383 (22), 364 (5), 349 (6), 321 (6), 307 (1), 216 (5), 200 (8), 186 (3), 172 (5), 157 (10),
131 (12), 105 (15), 91 (21).
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