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was eliminated by crystallization 'ice-bath cooling). The liquid phase was concentrated under reduced pressure
and submitted to CC 'hexane/AcOEt 9.1). The eluted fractions provided b-cyclocitral '2.5 g, 16 mmol) and g-
ionone, which was then further purified by distillation under reduced pressure to give pure 'Æ)-3 '18.1 g,
1
94 mmol; 72%; 98% chemical purity 'GC)). IR: 2932, 1675, 1364, 1254, 990, 895. H-NMR: 6.93 'dd, J 15.7,
10.1, HÀC'7)); 6.08 'd, J 15.7, HÀC'8)); 4.78 's, HÀCHC'5)); 4.53 's, HÀCHC'5)); 2.57 'd, J 10.1,
HÀC'6)); 2.33 ± 2.18 'm, HÀC'4)); 2.26 's, Me'10)); 2.13 ± 1.97 'm, HÀC'4)); 1.67 ± 1.26 'm, CH2'3), CH2'2));
0.89 's, MeÀC'1)); 0.85 's, MeÀC'1)). 13C-NMR: 198.3; 148.4; 147.2; 132.7; 109.6; 57.6; 38.6; 35.6; 34.1; 29.2;
27.3; 23.9; 23.1. MS: 192 '10, M ), 177 '31), 164 '13), 159 '14), 149 '100), 135 '13), 121 '70), 109 '54), 91 '27),
81 '49), 69 '48), 43 '57). Anal. calc. for C13H20O: C 81.20, H 10.48; found: C 81.25, H 10.50.
'Æ)-g-Ionol ''Æ)-12). NaBH4 '2.5 g, 66 mmol) reduction of racemic 3 '20 g, 104.2 mmol) in MeOH
'100 ml) afforded, after purification by CC 'hexane/AcOEt 8 :2), 12 '19.5 g, 100.5 mmol, 96%) as a 1:1 mixture
of two racemic diastereoisomers; 97% chemical purity 'GC). Chiral GC 'corresponding acetates): tR 19.05,
19.19, 19.26, 19.72.
Fractional Crystallization of the 4-Nitrobenzoates of 'Æ)-12 '4 stereoisomers). The ionol 12 '16 g,
82.5 mmol) in CH2Cl2 was treated with 4-nitrobenzoyl chloride '18.2 g, 98 mmol) and pyridine '20 ml). After
workup, the crude product was purified by CC 'hexane/AcOEt 9 :1) to give a racemic mixture of 4-
nitrobenzoates '25.9 g, 75.5 mmol; 91%). Three crystallizations from hexane afforded the crystalline racemic 4-
nitrobenzoate 13a '7.9 g, yield of recrystallizations 30%). M.p. 748. GC 'corresponding acetates): tR 19.05, 19.19;
de 98%. IR: 3418, 2927, 1717, 1524, 1338, 1277, 1104, 1037, 717. 1H-NMR: 8.34 ± 8.15 'm, 4 arom. H); 6.02 ± 5.90
'dd, J 14.7, 9.4, HÀC'7)); 5.71 ± 5.51 'm, HÀC'8), HÀC'9)); 4.75 's, HÀCHC'5)); 4.53 's, HÀCHC'5));
2.43 'd, J 9.4, HÀC'6)); 2.34 ± 2.21 'dt, J 13.5, 5.2, HÀC'4)); 2.10 ± 1.95 'm, HÀC'4)); 1.63 ± 1.24
'm, CH2'3), CH2'2)); 1.49 'd, J 6, Me'10)); 0.86 's, MeÀC'1)); 0.79 's, MeÀC'1)). MS: 343 '3, M ), 300
'22), 270 '3), 216 '6), 193 '19), 176 '40), 161 '41), 150 '100), 133 '37), 120 '83), 105 '51), 91 '63), 79 '34), 69
'74). Anal. calc. for C20H25NO4: C 69.95, H 7.34, N 4.08; found: C 70.05, H 7.38, N 4.15.
'Æ)-'6RS,9RS)-g-Ionol ''Æ)-13b). The crystalline 4-nitrobenzoate 13a '7.7 g, 22.5 mmol) was treated with
KOH '3 g, 53.5 mmol) in MeOH '60 ml) under reflux for 2 h. After the usual workup, the alcohol obtained was
purified by CC 'hexane/AcOEt 8 :2) to afford 'Æ)-13b '4.1 g, 21.1 mmol; 94%). GC 'corresponding acetates):
tR 19.05, 19.19; de 98%. IR: 3341, 2930, 1643, 1366, 1060, 980, 890. 1H-NMR: 5.81 ± 5.72 'dd, J 15.3, 9.4,
HÀC'7)); 5.58 ± 5.50 'dd, J 15.3, 6.3, HÀC'8)); 4.72 's, HÀCHC'5)); 4.53 's, HÀCHC'5)); 4.32
'quint., J 6.3, HÀC'9)); 2.41 'd, J 9.4, HÀC'6)); 2.30 ± 2.22 'dt, J 13.4, 5.4, HÀC'4)); 2.07 ± 1.98
'm, HÀC'4)); 1.65 ± 1.43 'm, 3 H); 1.46 's, OH); 1.36 ± 1.26 'm, 1 H); 1.27 'd, J 6.4, Me'10)); 0.9
's, MeÀC'1)); 0.81 's, MeÀC'1)). 13C-NMR: 203.8; 190.1; 182.9; 161.9; 130.9; 130.6; 130.3; 122.5; 110.8; 92.7;
88.8; 88.2; 83.1. MS: 194 '1, M ), 176 '17), 161 '35), 136 '100), 121 '87), 109 '60), 93 '65), 79 '44), 69 '72), 55
'25), 43 '78). Anal. calc. for C13H22O: C 80.35, H 11.41; found: C 80.43, H 11.48.
Enzymic Acetylation of 'Æ)-13b. A mixture of 'Æ)-13b '4 g, 20.6 mmol; de 99%), lipase PS 'Pseudomonas
cepacia; 4 g), and vinyl acetate '20 ml) in t-BuOMe '100 ml) was stirred at r.t. for 72 h. After filtration and
evaporation of the filtrate, the residue was chromatographed 'hexane/AcOEt 9 :1). The first-eluted fractions
afforded '6R,9R)-g-ionol acetate '14; 1.95 g, 8.3 mmol; 40%; 97% chemical purity 'GC)). Chiral GC: tR 19.19;
ee 99%. [a]2D0 77.3 'c 2, CHCl3). IR: 2932, 1739, 1369, 1241, 1044, 890. 1H-NMR: 5.88 ± 5.76 'dd, J 14.5,
9.7, HÀC'7)); 5.51 ± 5.29 'm, HÀC'8), HÀC'9)); 4.73 's, HÀCHC'5)); 4.51 's, HÀCHC'5)); 2.39 'd, J
9.7, HÀC'6)); 2.32 ± 2.20 'dt, J 13.9, 5.2, HÀC'4)); 2.11 ± 1.94 'm, HÀC'4)); 2.04 's, MeCOO); 1.68 ± 1.24
'm, CH2'3), CH2'2)); 1.31 'd, J 6.6, Me'10)); 0.87 's, MeÀC'1)); 0.79 's, MeÀC'1)). MS: 236 '2, M ), 203
'3), 193 '21), 176 '56), 161 '63), 133 '50), 119 '35), 105 '85), 91 '100), 79 '65), 69 '64), 55 '23), 43 '86). Anal.
calc. for C15H24O2: C 76.23, H 10.24; found: C 76.35, H 10.16.
The last-eluted fractions gave '6S,9S)-g-ionol '15; 1.8 g, 9.3 mmol; 45%; 96% chemical purity 'GC)).
Chiral GC 'corresponding acetate): tR 19.05; ee 95%. [a]2D0 2.2 'c 2, CHCl3). IR, 1H-NMR, MS: in
accordance with those of 'Æ)-13b. Anal. calc. for C13H22O: C 80.35, H 11.41; found: C 80.30, H 11.45.
'À)-g-Ionone ''À)-3). A sample of 14 '1 g, 4.2 mmol) was hydrolyzed with KOH '1 g, 18 mmol) in MeOH
'30 ml). The crude ionol obtained was then oxidized with MnO2 '2 g, 23 mmol) in CHCl3 '50 ml) under reflux
for 4 h. After filtration and evaporation of the filtrate, the residue was chromatographed 'hexane/AcOEt 9 :1).
Bulb-to-bulb distillation of the product afforded pure 'À)-3 '650 mg, 3.4 mmol; 81%; 98% chemical purity
'GC)). Chiral GC: tR 17.10; ee 99%. [a]D20 À37.4 'c 1, CHCl3), [a]2D0 À30.9 'c 0.5, EtOH). IR, 1H-NMR,
13C-NMR, MS: in accordance with those of 'Æ)-3. Anal. calc. for C13H20O: C 81.20, H 10.48; found: C 81.25,
H 10.50.
')-g-Ionone '')-3). A sample of 15 '1 g, 5.1 mmol) was oxidized with MnO2 '3 g, 34 mmol) in CHCl3
'50 ml) under reflux for 4 h. After filtration and evaporation of the filtrate, the residue was chromatographed