Novel 1,3-dioxanes from apple juice and cider

Article abstract of DOI:10.1021/jf990714x

Extracts obtained by XAD solid-phase extraction of apple juice and cider were separated by liquid chromatography on silica gel. Several new 1,3- dioxanes including the known 2-methyl-4-pentyl-1,3-dioxane and 2-methyl-4- [2'(Z)-pentenyl]-1,3-dioxane, were identified in the nonpolar fractions by GC/MS analysis and confirmed by chemical synthesis. The enantioselective synthesis of the stereoisomers of the 1,3-dioxanes was performed using (R)- and (R,S)-octane-1,3-diol and (R)- and (R,S)-5(Z)-octene-1,3-diol as starting material. Comparison with the isolated products indicated that the natural products consisted of a mixture of (2S,4R) and (2R,4R) stereoisomers in the ratio of approximately 10:1, except for 1,3-dioxanes generated from acetone and 2-butanone. It is assumed that the 1,3-dioxanes are chemically formed in the apples and cider from the natural apple ingredients (R)-octane-1,3-diol, (R)-5(Z)-octene-1,3-diol, (3R,7R)- and (3R,7S)-octane-1,3,7-triol, and the appropriate aldehydes and ketones, which are produced either by the apples or by yeast during fermentation of the apple juice.

Full text of DOI:10.1021/jf990714x

5178
J. Agric. Food Chem. 1999, 47, 5178−5183
Novel 1,3-Dioxa n es fr om Ap p le J u ice a n d Cid er
Dominique Kavvadias, Till Beuerle, Martina Wein, Barbara Boss, Thorsten Ko¨nig, and
Wilfried Schwab*
Lehrstuhl fu¨r Lebensmittelchemie, Universita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany
Extracts obtained by XAD solid-phase extraction of apple juice and cider were separated by liquid
chromatography on silica gel. Several new 1,3-dioxanes including the known 2-methyl-4-pentyl-
1,3-dioxane and 2-methyl-4-[2′(Z)-pentenyl]-1,3-dioxane, were identified in the nonpolar fractions
by GC/MS analysis and confirmed by chemical synthesis. The enantioselective synthesis of the
stereoisomers of the 1,3-dioxanes was performed using (R)- and (R,S)-octane-1,3-diol and (R)- and
(R,S)-5(Z)-octene-1,3-diol as starting material. Comparison with the isolated products indicated that
the natural products consisted of a mixture of (2S,4R) and (2R,4R) stereoisomers in the ratio of
approximately 10:1, except for 1,3-dioxanes generated from acetone and 2-butanone. It is assumed
that the 1,3-dioxanes are chemically formed in the apples and cider from the natural apple
ingredients (R)-octane-1,3-diol, (R)-5(Z)-octene-1,3-diol, (3R,7R)- and (3R,7S)-octane-1,3,7-triol, and
the appropriate aldehydes and ketones, which are produced either by the apples or by yeast during
fermentation of the apple juice.
Keyw or d s: Apple; cider; 1,3-dioxane; acetal; stereoisomers
INTRODUCTION
French apple varieties (Beuerle et al., 1996) used for
cider production contain large amounts of 1 and 3, and
2 was recently identified in the variety Peau de Chien
(Beuerle et al., 1999). Because yeast (Dittrich, 1987) and
apples (Paillard, 1990) produce a number of aldehydes
such as propanal, butanal, 2-methylpropanal, hexanal,
3-methylbutanal, and 2-methylbutanal, as well as the
ketones acetone and 2-butanone, we expected the oc-
currence of 1,3-dioxanes derived from 1,3-diols and these
carbonyl compounds in apples and cider. This paper
describes the chemical synthesis of 4-22, the determi-
nation of their absolute configuration and conformation,
and the identification of 1,3-dioxanes in apples and
cider.
Recently, the natural occurrence of (2S,4R)- and
(2R,4R)-2-methyl-4-pentyl-1,3-dioxane 4 as well as
(2S,4R)- and (2R,4R)-2-methyl-4-[2′(Z)-pentenyl]-1,3-
dioxane 14 in cider has been reported (Dietrich et al.,
1997). It was assumed that the 1,3-dioxanes were
formed in cider by chemical reactions between acetal-
dehyde and (R)-octane-1,3-diol (1) and (R)-5(Z)-octene-
1,3-diol (3), respectively. Compounds 1 and 3 have been
EXPERIMENTAL PROCEDURES
Gen er a l P r oced u r es. 1H and 13C NMR spectra were re-
corded on a 250 MHz/63 MHz or 400 MHz/100 MHz spectrom-
eter (Bruker). All NMR data are reported in parts per million
(δ) downfield from the internal standard TMS or solvent
signals (CDCl3, δH/C 7.27/77.0). Silica gel 60 (0.063-0.2 mm)
was used for flash chromatography. Solvents were redistilled
before use. The purities of the compounds were shown to be
g90% by 1H NMR, TLC, and/or GC/MS. An HP 5890-2 gas
chromatograph with FID was used for the GC analyses. Split
injection (1:20) was employed. The GC was equipped either
with a J &W fused silica DB-Wax capillary column (30 m ×
0.25 mm, df ) 0.25 µm), with a DB-5 capillary column (30 m
× 0.25 mm, df ) 0.25 µm), or with a 30% 2,3-O-diethyl-6-O-
tert-butyldimethylsilyl-â-CD/PS086 column (25 m × 0.25 mm,
df ) 0.15 µm) for the separation of the enantiomers. The tem-
perature program for the DB-Wax capillary column was as
follows: 3 min isothermal at 50 °C, increased from 50 to 240
°C at 4 °C/min. The temperature program for the DB-5 capil-
lary column was from 60 to 300 °C at 5 °C/min and then held
for 10 min at this temperature. Helium was used as carrier
gas (2.0 mL/min). Calculation of retention indices for the DB-
Wax column (Ri) was conducted on the basis of n-hydrocarbons
with the aid of an additional BASIC program (Baugh, 1993).
The temperature program for the 2,3-O-diethyl-6-O-tert-bu-
tyldimethylsilyl-â-CD/PS086 column was 1 min isothermal at
identified in juice from a number of apple (Beuerle et
al., 1996; Berger et al., 1988) and pear (Beuerle and
Schwab, 1997) cultivars and in the mountain papaya
fruit (Carica pubescens) (Krajewski et al., 1997). Acet-
aldehyde is one of the major products formed by yeast
during fermentation of apple juice (Dittrich, 1987).
* Corresponding author (telephone +931-888-4651; fax +931-
888-5484; e-mail schwab@pzlc.uni-wuerzburg.de).
10.1021/jf990714x CCC: $18.00 © 1999 American Chemical Society
Published on Web 11/13/1999

1,3-Dioxanes from Apple Products
J. Agric. Food Chem., Vol. 47, No. 12, 1999 5179
2R,4R
Ta ble 1. Ri Va lu es a n d EIMS Da ta of 1,3-Dioxa n es 5-13
Ri
2S,4R
Ri
5
6
7
8
9
1477
69 (100), 57 (42), 55 (41), 111 (26), 86 (22), 58 (15),
157 (13), 115 (6), 185 (3)
1560
69 (100), 55 (40), 57 (26), 111 (21), 115 (21), 73 (18),
157 (13), 59 (11), 43 (11), 67 (5), 83 (4), 185 (3)
69 (100), 55 (48), 111 (40), 157 (23), 129 (20), 57 (18),
43 (15), 73 (10), 87 (7), 83 (6), 199 (2)
69 (100), 55 (55), 111 (38), 157 (20), 57 (19), 129 (15),
83 (11), 73 (10), 70 (8), 67 (8), 112 (4), 158 (3), 199 (2)
69 (100), 157 (70), 111 (65), 55 (47), 57 (14), 83 (12),
70 (8), 158 (7), 85 (6), 99 (5), 227 (3)
1568
1471
1765
1606
69 (100), 111 (53), 55 (47), 157 (29), 71 (27), 100 (22),
43 (19), 57 (18), 72 (10), 83 (8), 129 (7), 199 (6)
69 (100), 55 (55), 111 (43), 71 (26), 157 (20), 57 (18),
100 (15), 83 (12), 72 (11), 112 (6), 129 (5), 199 (3)
69 (100), 111 (67), 157 (48), 55 (53), 99 (25), 57 (16),
83 (15), 71 (10), 128 (8), 158 (6), 85 (5), 227 (5)
69 (100), 111 (48), 55 (35), 157 (27), 85 (24), 57 (20),
71 (11), 83 (9), 114 (8), 112 (6), 99 (5), 158 (5),
213 (4), 143 (4), 127 (2)
1649
1565
1847
1678
69 (100), 111 (36), 55 (30), 157 (20), 57 (15), 143 (10),
71 (9), 67 (7), 83 (5), 87 (4), 85 (4), 158 (3),
213 (1), 127 (1)
10
11
1575
1429
69 (100), 111 (43), 55 (35), 57 (24), 157 (23), 85 (15),
58 (12), 83 (7), 67 (7), 114 (5), 213 (3), 143 (3),
158 (3), 127 (1)
1660
69 (100), 111 (40), 55 (35), 157 (18), 57 (17), 85 (12),
67 (8), 70 (7), 83 (6), 143 (5), 114 (4), 213 (2),
158 (3), 127 (1)
69 (100), 171 (33), 111 (32), 59 (31), 55 (30), 58 (14),
57 (13), 115 (12), 86 (10), 70 (8), 73 (7), 67 (7),
172 (5), 110 (4), 83 (4), 82 (4), 81 (4), 129 (2)
69 (100), 55 (36), 57 (30), 73 (27), 111 (25), 185 (14),
72 (11), 129 (7), 67 (7), 171 (6), 100 (5), 83 (4), 81 (3)
43 (100), 45 (88), 67 (65), 57 (58), 55 (53), 72 (50),
101 (42), 109 (30), 71 (29), 59 (24), 81 (27),
54 (23), 69 (16), 83 (15), 99 (12), 127 (10),
97 (10), 85 (9), 98 (8), 93 (7), 111 (5), 79 (4), 173 (4),
126 (4), 155 (2), 187 (1)
12
13
1485
2067
1516
2157
69 (100), 55 (37), 111 (27), 73 (20), 171 (20), 57 (15),
67 (8), 129 (6), 100 (5), 83 (5), 172 (4), 81 (4)
43 (100), 67 (72), 55 (66), 72 (60), 57 (56), 45 (50),
101 (40), 59 (39), 71 (38), 81 (36), 127 (20),
69 (18), 54 (16), 70 (15), 109 (14), 68 (14), 83 (11),
85 (10), 79 (8), 97 (7), 98 (7), 116 (4), 102 (4), 99 (4),
173 (3), 143 (3), 187 (1)
Ta ble 2. Ri Va lu es a n d EIMS Da ta of 1,3-Dioxa n es 15-22
Ri
2S,4R
Ri
2R,4R
15
16
17
18
1537
115 (100), 73 (100), 67 (85), 57 (85), 59 (67), 109 (62),
55 (50), 69 (27), 81 (26), 79 (15), 93 (14),
53 (14), 97 (10), 85 (8), 77 (7), 82 (7), 116 (6),
110 (5), 183 (4), 184 (3), 144 (3), 126 (3), 124 (3)
55 (100), 67 (93), 109 (78), 57 (76), 129 (73), 87 (47),
81 (29), 71 (29), 93 (17), 79 (17), 53 (13),
69 (12), 68 (10), 155 (9), 83 (8), 110 (6), 77 (6),
97 (5), 197 (5), 126 (4), 198 (4)
67 (100), 109 (84), 55 (78), 58 (57), 129 (46), 73 (46),
83 (28), 81 (26), 85 (14), 71 (14), 79 (13),
1616
115 (100), 73 (77), 57 (60), 59 (58), 67 (55), 109 (25),
55 (25), 81 (15), 69 (13), 79 (8), 54 (7), 52 (7),
116 (5), 155 (5), 183 (1)
1631
1522
1834
1708
1600
1909
55 (100), 129 (86), 67 (78), 57 (76), 73 (56), 87 (45),
109 (42), 81 (20), 71 (15), 79 (12), 53 (12),
155 (10), 69 (8), 83 (8), 77 (6), 93 (5), 130 (5), 197 (1)
67 (100), 55 (94), 129 (73), 57 (70), 109 (46), 73 (46),
83 (23), 53 (23), 71 (22), 155 (20), 85 (17), 45 (8),
87 (7), 69 (7), 77 (6), 67 (6), 111 (6), 65 (5), 130 (3),
107 (3), 197 (1)
55 (100), 67 (79), 157 (63), 109 (60), 57 (57), 83 (48),
85 (42), 73 (33), 81 (20), 69 (20), 155 (15),
87 (12), 99 (7), 95 (6), 93 (6), 97 (5), 158 (4), 110 (4),
139 (3), 225 (1)
93 (11), 69 (10), 53 (10), 155 (8), 87 (7), 110 (6),
198 (5), 197 (5), 111 (5), 130 (4), 169 (1)
109 (100), 55 (100), 67 (94), 57 (61), 57 (61), 83 (55),
157 (52), 85 (43), 73 (32), 81 (28), 69 (26),
93 (18), 79 (15), 71 (15), 155 (15), 87 (12),
53 (11), 115 (9), 99 (9), 97 (8), 95 (8), 158 (5),
225 (4), 126 (4), 124 (3), 101 (3), 226 (2)
19
20
21
22
1663
1636
1487
1550
67 (100), 69 (84), 109 (77), 71 (50), 143 (48), 57 (46),
55 (39), 87 (27), 81 (26), 101 (16), 79 (16), 93 (15),
108 (13), 83 (12), 54 (12), 155 (11), 85 (10),
97 (6), 144 (5), 212 (4), 211 (3), 126 (3), 125 (3)
67 (100), 109 (72), 69 (53), 57 (30), 55 (29), 81 (26),
45 (21), 143 (19), 71 (16), 79 (15), 73 (15),
155 (13), 93 (9), 108 (9), 110 (7), 97 (6), 99 (5),
212 (4), 125 (3), 101 (3), 126 (2)
115 (100), 67 (92), 59 (78), 73 (45), 57 (40), 109 (38),
55 (27), 81 (23), 169 (20), 58 (12), 54 (12),
108 (11), 97 (10), 69 (9), 68 (9), 116 (8), 93 (7),
110 (5), 170 (3),126 (3), 91 (3)
1743
1723
69 (100), 67 (95), 143 (68), 109 (65), 71 (55), 57 (54),
55 (39), 87 (36), 81 (21), 101 (17), 79 (16),
155 (15), 85 (9), 83 (7), 77 (7), 144 (6), 93 (5), 97 (4),
125 (3), 95 (3), 212 (3), 211 (3)
67 (100), 69 (93), 109 (69), 143 (55), 57 (50), 55 (42),
73 (27), 71 (27), 81 (23), 79 (17), 155 (15), 53 (14),
54 (14), 87 (13), 75 (10), 85 (8), 77 (7), 97 (6),
144 (6), 125 (5), 99 (5), 101 (4), 212 (1), 211 (1)
67 (100), 73 (60), 109 (46), 57 (45), 129 (40), 55 (38),
81 (21), 183 (13), 79 (10), 169 (8), 68 (8), 54 (8),
110 (6), 108 (6), 93 (6), 77 (6), 130 (4), 97 (4), 91 (4)
1570
67 (100), 109 (46), 73 (47), 55 (40), 169 (23), 129 (22),
81 (18), 57 (18), 79 (10), 68 (7), 54 (7), 69 (5), 77 (4),
110 (4), 93 (4), 91 (3)
80 °C, increased from 80 to 190 °C at 1.5 °C/min. Helium was
used as carrier gas (65 kPa). GC/MS was performed with a
Fisons 8000 gas chromatograph with a split injector (1:30)
coupled to the Fisons MD mass spectrometer and MassLab
data system. The temperature program was as follows: 3 min
isothermal at 50 °C, increased from 50 to 240 °C at 4 °C/min.
Conditions of the mass spectrometer: temperature of the ion
source, 230 °C; temperature of all connection parts, 200 °C;
electron energy, 70 eV; cathodic current, 4 mA; mass range,
40-250 or 40-499 Da.
resin (Beuerle et al., 1997). The resin was eluted with Et2O
and the extract further fractionated by flash chromatography
on silica gel using pentane/Et2O mixtures of increasing polar-
ity. Fractions were monitored by GC, GC/MS and TLC on silica
gel. The TLC was developed in pentane/Et2O (9:1) and visual-
ized by spraying with 1% vanillin in H2SO4 (concentrated).
(R,S)-Octa n e-1,3-d iol (r a c-1). The preparation was per-
formed in the same manner as reported (Beuerle et al., 1996).
Spectral data were in accordance with previously published
values (Berger et al., 1988; Schwab et al., 1989).
P la n t Ma ter ia l. Apple fruits, cv. Peau de Chien, and
French cider were kindly provided by Pernod Ricard, France.
Extr a ction a n d Isola tion . Apple juice (2.5 kg) or cider (8
L) was subjected to solid-phase extraction on Amberlite XAD-2
3(Z)-Hexen yl Ch lor id e. Thionyl chloride (31.65 g, 0.266
mol) was added to a solution of 3(Z)-hexenoic acid (15.16 g,
0.133 mol) in benzene (50 mL), and the mixture was stirred
for 4 h at room temperature (Smith et al., 1984). Excess of

5180 J. Agric. Food Chem., Vol. 47, No. 12, 1999
Kavvadias et al.
Ta ble 3. 13C NMR Da ta of Dioxa n es 5-13 a n d 15-22a
carbon
C2
5
6
7
8
9
10
11
12
13
15
16
17
18
20
19
21
22
103.2 102.0 105.9 102.3 101.2 105.2
105.4
98.2 99.0 98.9 103.0 102.0 105.7 102.3 104.9 101.2
99.4
68.9 68.3 76.5
68.6
36.5 36.5 35.8
36.6
60.0 59.5 66.4
59.9
98.2
99.5
100.4
68.4
68.6
34.4
35.6
59.5
59.8
30.7
31.1
C4
76.8
36.1
66.7
31.8
24.7
31.6
22.6
14.0
28.3
8.4
76.7
36.1
66.7
31.8
24.7
31.6
22.6
14.0
37.3
17.5
13.9
76.7
36.1
66.7
31.7
24.7
31.6
22.6
13.9
32.9
17.1
17.1
76.8
36.1
66.7
31.8
24.7
31.6
22.6
13.9
35.2
23.8
31.7
22.6
14.0
76.7
36.0
66.6
31.7
24.6
31.6
22.5
13.9
43.9
23.9
22.8
22.8
77.0
36.4
67.0
32.1
76.4
33.8
66.5
31.1
76.4
33.8
66.6
31.1
76.4
33.9
66.6
31.2
76.5
33.9
66.6
31.1
76.4
33.9
60.6
31.2
76.5
33.8
66.6
31.1
68.9
34.3
60.0
30.9
C5
C6
C7
31.8 31.6 31.0
31.8
C8
24.6
24.7
32.0
24.6 24.6 23.4 123.7 123.7 123.9 123.8 124.0 123.8 123.8 123.9
24.7
C9
31.4 31.2 39.1 133.9 133.9 133.8 134.0 133.8 133.9 133.9 133.8
133.9
22.6 22.6 67.8
22.5
C10
C11
C12
C13
C14
C15
22.9
14.3
20.6
14.0
28.2
8.4
20.7
14.1
37.2
17.3
13.9
20.7
14.1
32.9
17.1
17.1
20.7
14.1
35.2
23.8
31.7
22.5
13.9
20.7
14.1
39.5
20.6
20.7
20.7
14.0 13.9 21.2
14.1
14.1
14.0
14.1
34.1
34.3
17.3
21.3
23.8
26.3
39.7 a 30.0 35.7 21.1
39.8 e 19.3 36.1
25.0
43.9 a 30.0
e 19.2
23.9
17.2
21.2
23.9
26.1
24.2
24.3
11.4
11.6
11.7
14.0
14.1
22.9
22.7
13.6
C16
a
a, axial; e, equatorial.
thionyl chloride and benzene was removed (100 mbar, 40 °C),
and the product was distilled (3 mbar, 45-47 °C): 12.0 g (0.091
mol, 68%), IR(KBr) νmax 3010 (CdC), 2950 (CH3), 2880 (CH3),
2910 (CH2), 2850 (CH2), 1785 (CdO), 735 [dC-H of (Z)-double
bond].
(-CH2OSO2-, t, 2.21 Hz), 7.34 and 7.81 (PhH, d, 8.2 Hz); 13
C
NMR (CDCl3, 100 MHz) δ 12.3 (H3CCH2Ct), 13.1 (H3CCH2-
), 21.5 (CH3Ph), 58.7 (-CH2OSO2-), 71.2 (CH2CtC), 128.1,
129,7, 144.8 (C6H4); EIMS m/z 91 (100), 139 (75), 65 (60), 92
(43), 66 (40), 83 (20), 67 (15), 117 (12), 155 (10).
Ma lon ic Acid Mon oeth yl Ester . Potassium ethyl mal-
onate (25 g, 0.147 mol) was dissolved in H2O (16 mL) and
cooled (5 °C). Concentrated HCl (12.5 mL) was carefully added
to the aqueous mixture while the temperature was maintained
below 10 °C (Strube, 1993). The resulting precipitate was
removed by filtration and washed with Et2O (75 mL). The
aqueous solution was extracted (three times) with Et2O. The
organic extracts were combined and dried (Na2SO4), and the
solvent was removed in vacuo to yield the ester: 19.1 g (0.145
mol, 99%); IR(KBr) νmax 3500-2600 (OH), 2960 (CH3), 2925
(CH2), 1710 (CdO), 1730 (CdO), 1360, 1145, 950.
Eth yl 3-Oxo-5(Z)-octen oa te. Monoethyl ester (19.1 g,
0.145 mol) and 2,2′-bipyridine (5 mg) were dissolved in THF
(250 mL) under argon and cooled to -65 °C. N-Butyllithium
(∼0.3 mol) dissolved in hexane was carefully added until the
indicator remained pink and the temperature increased to -5
°C. The solution was cooled to -65 °C, and 3(Z)-hexenoic
chloride (10.43 g, 0.079 mol) was added dropwise (Wierenga
and Skulnick, 1979). After 15 min of stirring at -65 °C, the
mixture was poured in a mixture of Et2O (400 mL) and 1 N
HCl (200 mL). The organic layer was washed twice with
saturated NaHCO3 solution (100 mL) and H2O (100 mL). The
extract was dried (Na2SO4), and ethyl 3-oxo-5(Z)-octenoate was
distilled in vacuo to yield the octenoate: 12.2 g (0.066 mol,
84%); spectral data were identical with previously published
data (Beuerle et al., 1996; Berger et al., 1988).
1-Br om o-2-p en tyn e. Nucleophilic substitution of 1-tosyl-
2-pentyne with NaBr yielded 1-bromo-2-pentyne (Ishchenko
et al., 1987): yield, 50% for both steps; Rf 0.57 [n-hexane/
EtOAc (95:5)]; Ri 1301; IR(KBr) νmax 3010 (CdCH), 2950 (CH),
2910 (CH), 2850 (CH), 2210 (CdC), 600 (CBr); 1H NMR
(CDCl3, 400 MHz) δ 1.14 (H3C-, t, 7.35 Hz), 2.25 (CH3CH2Ct
, m), 3.93 (tCCH2Br, t, 2.39 Hz); 13C NMR (CDCl3, 100 MHz)
δ 12.6 (H3CCH2Ct), 13.4 (H3CCH2-), 15.5 (tCCH2Br), 74.7
(-CH2Ct), 89.4 (CtCCH2Br); EIMS m/z 67 (100), 65 (14), 148
[M]+ (13), 68 (12), 146 (12).
2,5-Octa d iin ol. 1-Bromo-2-pentyne and 2-(propargyloxy)-
tetrahydropyran were coupled according to the procedure of
Kobayashi et al. (1989), Mori and Ebata (1986), and Cossey
and Aclinou (1990): yield, 73%; Ri 2113; EIMS, m/z 77 (100),
91 (60), 104 (55), 79 (45), 65 (40), 103 (30), 51 (30), 53 (25), 63
(23), 107 (15), 93 (12); 1H and 13C NMR were in accordance
with previously published data (Kobayashi et al., 1989; Mori
and Ebata, 1986; Cossey and Aclinou, 1990; Nigam and
Weedon, 1956).
2(Z),5(Z)-Octa d ien ol. Reduction of 2,5-octadiinol according
to Lindlar’s method was performed in the same manner as
reported (Kobayashi et al., 1989; Mori and Ebata, 1986; Cossey
and Aclinou, 1990; Nigam and Weedon, 1956; Lindlar and
Dubius, 1966). The product was purified by flash chromatog-
raphy on silica gel with pentane/Et2O (7:3): yield, 86%; Rf 0.29
[Et2O/pentane (3:7)]; Ri 1681; EIMS, m/z 79 (100), 55 (45), 67
(39), 77 (25), 93 (25), 70 (21), 53 (18), 80 (15), 91 (15), 108 [M
- H2O]+ (15).
(2S,3R)-Ep oxy-5(Z)-octen ol. Epoxidation of 2(Z),5(Z)-oc-
tadienol was conducted according to the method of Katsuki
and Sharpless (1980) as described by Beuerle et al. (1996):
yield, 97%; Rf 0.75 (Et2O); Ri 1998; EIMS, m/z 67 (100), 55
(90), 111 (70), 81 (65), 69 (47), 53 (43), 79 (43), 57 (40), 93 (38),
83 (34), 77 (25), 65 (21), 91 (18).
(R,S)-5(Z)-Octen e-1,3-d iol (r a c-3). Ethyl 3-oxo-5(Z)-oct-
enoate (5.2 g, 0.029 mol) was reduced by LiAlH4 in absolute
Et2O. 2.9 g (0.02 mol, 69%). Spectral data were in accordance
with previously published data (Beuerle et al., 1996; Berger
et al., 1988).
(R)-Octa n e-1,3-d iol (R-1). Compound R-1 was synthesized
according to the method of Dietrich et al. (1997). EIMS, Ri,
1
and H and 13C NMR were identical with previously published
data (Beuerle et al., 1996).
(R)-5(Z)-Octen e-1,3-d iol (R-3). Red-Al-solution [65% in
toluene (12 mL, 39 mmol)] (Sugiyama et al., 1990) was added
dropwise to a cooled (0 °C) solution of (2S,3R)-epoxy-5(Z)-octen-
1-ol (2.6 g, 0.019 mol) in THF (100 mL) until no more formation
of gas was detectable. The mixture was stirred for 8 h at 0 °C,
1-Tosyl-2-p en tyn e. 2-Pentyne-1-ol was tosylated according
to a published procedure (Ishchenko et al., 1987): Rf 0.78
1
(Et2O); Ri 1900; H NMR (CDCl3, 400 MHz) δ 1.01 (H3CCH2,
t, 7.36 Hz), 2.04-2.12 (CH3CH2Ct, m), 2.45 (CH3Ph, s), 4.69

1,3-Dioxanes from Apple Products
J. Agric. Food Chem., Vol. 47, No. 12, 1999 5181
and the reaction was stopped with 10% HCl (100 mL). The
aqueous phase was extracted (three times) with Et2O (50 mL).
The organic layers were combined, dried (Na2SO4), and
concentrated. The product was purified by flash chromatog-
raphy on silica gel with Et2O/pentane (7:3) and Et2O. The ratio
1,3-diol/1,2-diol was 95:5: 1.95 g (0.014 mol, 76%); IR, 1H and
13
C NMR, Ri, and EIMS were in accordance with previously
published data (Beuerle et al., 1996).
Gen er a l P r ep a r a tion of 1,3-Dioxa n es. Diol (2 mmol),
aldehyde or ketone (2 mmol), p-toluenesulfonic acid (6 mg),
and Na2SO4 (40 mg) were suspended in Et2O, and the mixture
was stirred overnight until the diol completely disappeared.
1,3-Dioxanes were purified by flash chromatography with
pentane/Et2O (9:1) on silica gel (Dietrich et al., 1997): yields,
0.25-0.35 g (1.4-1.9 mmol, 70-95%); Ri and EIMS (cf. Tables
1
1-2); H and 13C NMR (cf. Tables 3-5).
RESULTS AND DISCUSSION
During our investigation on the biogenesis of (R)-
octane-1,3-diol [(R)-1] and (R)-5(Z)-octene-1,3-diol [(R)-
3] in apples and pears we identified (2S,4R)- and
(2R,4R)-2-methyl-4-pentyl-1,3-dioxane 4 as well as
(2S,4R)- and (2R,4R)-2-methyl-4-[2′(Z)-pentenyl]-1,3-
dioxane 14 for the first time in apple products such as
cider (Dietrich et al., 1997). However, we expected the
occurrence of further 1,3-dioxanes formed from 1,3-diols
and carbonyl compounds because yeast and apples
produce a number of aldehydes and ketones. Therefore,
reference compounds were prepared to identify the
anticipated 1,3-dioxanes.
(R,S)-Octane-1,3-diol [(R,S)-1] and (R,S)-5(Z)-octene-
1,3-diol [(R,S)-3] were synthesized by LiAlH4 reduction
of their respective 3-oxo ethyl esters, whereas (R)-
octane-1,3-diol [(R)-1] and (R)-5(Z)-octane-1,3-diol [(R)-
3] were obtained by Sharpless epoxidation of their allylic
alcohols using (+)-diethyl tartrate as the chiral ligand
(Dietrich et al., 1997). The synthesis of (3R,7R)- and
(3R,S,7R,S)-octan-1,3,7-triol denoted, respectively, as
[(3R,7R)- and (3R,S,7R,S)-2) has been reported recently
(Beuerle et al., 1999). The (4R,S,2R,S) stereoisomers of
4-10, 12-20, and 22 were obtained by the reaction of
racemic 1,3-diols with the aldehydes or ketones, and
(4R,2R,S) diastereomers were formed from (3R)-diols
and the aldehydes or ketones. Tables 1-5 show the
1
mass spectra and 13C and H NMR data. Separation of
the diastereomers by flash chromatography on silica gel
afforded pure (4R,2R)- and (4R,2S)-1,3-dioxanes in a
ratio of approximately 1:10, except for 11 and 21 as they
did not appear as diastereomers. However, separation
of stereoisomers of 12 and 22 was not achieved by flash
chromatography on silica gel. GC analysis revealed a
ratio of 2:3 for (4R,2R)-12/(4R,2S)-12 and (4R,2R)-22/
1
(4R,2S)-22. H NMR homonuclear decoupling experi-
ments of (4R,2S)-4 and (4R,2S)-14 showed vicinal
coupling between 4-H and 5-H axial (J ) 12 Hz) and
5-H equatorial, respectively (J ) 1 Hz). These are typical
coupling constants for axial protons, and they are
inconsistent with the presence of equatorial protons at
position 4 (Dietrich et al., 1997; Eliel and Knoeber,
1968). The configuration at carbon 2, originating from
the carbonyl carbon of the aldehydes, is determined by
the disposition of the 2-alkyl group, which prefers the
equatorial position (Eliel and Knoeber, 1968). NOE
experiments of (4R,2S)-1,3-dioxanes showed positive
enhancement of H-6 axial and H-4 after irradiating H-2
and vice versa. Consequently, protons at positions 2, 4,
and 6axial are all axial, confirming the chair conforma-
tion of the 1,3-dioxanes and the (S)-configuration at

5182 J. Agric. Food Chem., Vol. 47, No. 12, 1999
Kavvadias et al.
F igu r e 1. Fragmentation pattern of 1,3-dioxanes.
Ta ble 6. 1,3-Dioxa n es in Ap p les a n d Cid er
1,3-dioxane
apple
cider
1,3-dioxane
apple
cider
4
5
6
7
8
++
+
+++
++
+
14
15
16
17
18
19
20
21
22
+
++
+
nd
nd
nd
+
+
+
nd
+
nd
nd
nd
nd
nd
+
+
+
+
9
++
+
nd
nd
nd
nd
+
10
11
12
13
+
+
+
++
+
+
a
nd, not detected; +, 0.001-0.1 mg/L; ++, 0.1-1 mg/L; +++,
>1 mg/L.
position 2 as expected for the major products (Dietrich
et al., 1997). The minor compounds were assigned as
(4R,2R)-1,3-dioxanes on the basis of their chromato-
graphic behavior and mass spectra.
The mass spectra of the 1,3-dioxanes showed char-
acteristic fragmentation patterns (Figure 1). Cleavage
between C2/R1 and C2/R2 as well as C4/R3 was preferred.
Acetals displayed the [M - H]+ ion, which was not
detected for the ketals. Aldehydic characteristic m/z
fragments based on the R1 substituent were obtained.
The pentyl- and 2(Z)-pentenyl moieties were indicated
by the fragment ions m/z 111 and 109, which served to
distinguish 1,3-dioxanes from 1 and 3, respectively
(Figure 1).
Compounds 4-22, ranging in concentration from 10-3
to 10 ppm, were detected by GC/MS analysis in extracts
of apples and cider aged for one year (Table 6). The
configuration at carbon 4′ in naturally occurring 13 was
deduced by multidimensional gas chromatographic
(MDGC) analysis by comparison with the synthesized
reference compounds. A ratio of 4′R/4′S in 13 of 3:2
corresponding to the enantiomeric ratio in naturally
occurring 2 at position 7 was found (Beuerle et al.,
1999).
Therefore, we believe that the 1,3-dioxanes are chemi-
cally formed from the natural apple ingredients (R)-
octane-1,3-diol, (R)-5(Z)-octene-1,3-diol, (3R,7R)- and
(3R,7S)-octane-1,3,7-triol and the respective aldehydes
and ketones, which are produced either by the apples
(Paillard 1990) or by the yeast fermentation of the apple
juice. The dioxanes exhibit a weak “green note“ flavor
so they might contribute to the overall flavor of cider
by decreasing the concentration of undesirable alde-

1,3-Dioxanes from Apple Products
J. Agric. Food Chem., Vol. 47, No. 12, 1999 5183
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ABBREVIATIONS USED
FID, flame ionization detector; GC, capillary gas
chromatography; GC/MS, capillary gas chromatography/
mass spectrometry; HPLC, high-performance liquid
chromatography; TLC, thin-layer chromatography: XAD,
polystyrene resin.
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