Synthesis of deuterated γ-lactones for use in stable isotope dilution assays

Article abstract of DOI:10.1021/jf048885b

Two syntheses of deuterated γ-lactones for use as internal standards in stable isotope dilution assays (SIDA) were developed. [2,2,3,3- ²H₄]-γ-Octa-, -γ-deca-, and -γ-dodecalactones with >89% deuterium incorporation were prepared in 27, 17, and 19% overall yields, respectively, by the reduction of a doubly protected hydroxypropiolic acid with deuterium gas. [3,3,4-²H ₃]-γ-Octa- and -γ-dodecalactones were prepared in 6 and 23% yields with >92% deuterium incorporation by the free radical addition of 2-iodoacetamide to [1,1,2-²H₃]-1-hexene and [1,1,2- ²H₃]-1-decene, respectively. Reaction yields were highly dependent upon the purity of the 1-alkene starting material. The deuterated γ-lactones were evaluated as internal standards for SIDA.

Full text of DOI:10.1021/jf048885b

J. Agric. Food Chem. 2004, 52, 7075−7083 7075
Synthesis of Deuterated
γ
-Lactones for Use in Stable Isotope
Dilution Assays
JO-ANNA HISLOP, MARTIN B. HUNT, SIMON FIELDER, AND DARYL D. ROWAN*
The Horticulture and Food Research Institute of New Zealand Ltd., Private Bag 11030,
Palmerston North, New Zealand
Two syntheses of deuterated γ-lactones for use as internal standards in stable isotope dilution assays
2
(
SIDA) were developed. [2,2,3,3- H
4
]-γ-Octa-, -γ-deca-, and -γ-dodecalactones with >89% deuterium
incorporation were prepared in 27, 17, and 19% overall yields, respectively, by the reduction of a
2
doubly protected hydroxypropiolic acid with deuterium gas. [3,3,4- H
3
]-γ-Octa- and -γ-dodecalactones
were prepared in 6 and 23% yields with >92% deuterium incorporation by the free radical addition
2
2
3 3
of 2-iodoacetamide to [1,1,2- H ]-1-hexene and [1,1,2- H ]-1-decene, respectively. Reaction yields
were highly dependent upon the purity of the 1-alkene starting material. The deuterated γ-lactones
were evaluated as internal standards for SIDA.
KEYWORDS: γ-Lactones; deuterium; synthesis; isotope labeling; SIDA; flavor compounds; γ-dodeca-
lactone; γ-decalactone; γ-octalactone
INTRODUCTION
spectrum (Scheme 1). For maximum sensitivity in SIDA, a
deuterium label should therefore be placed in the lactone ring.
γ-Lactones (Scheme 1) are important flavor compounds that
occur in a wide range of foods including stone fruit (1, 2), wine
Although many syntheses of γ-lactone have been developed
9), few are suitable for the introduction of multiple deuterium
(
(
3), milk (4), and dairy products (5). γ-Lactones are formed by
the cyclization of the corresponding γ-hydroxycarboxylic acids
6), with the even-numbered carbon chain lactones predominat-
atoms regioselectively into the lactone ring. Heiba et al. (10)
have reported the synthesis of a range of γ-lactones via a one-
step procedure involving the addition of substituted carboxylate
salts to alkenes at elevated temperatures in the presence of
manganese(III) salts. Curran and Ko (11) reported the one-step
synthesis of multiply substituted γ-lactones by the free radical
addition of 2-bromoacetic acid derivatives to butyl vinyl ether.
Yorimitsu et al. (12) have used Curran’s atom transfer process
and reported the isolation of γ-lactones in good yields from
the addition of a 2-iodocarbonyl compound to a 1-alken-ω-ol
in water in the presence of a radical initiator. Thus, 2-iodo-
acetamide and 5-hexen-1-ol were reacted in water in the
presence of a radical initiator to give 8-hydroxy-γ-octalactone
in 95% yield. The reaction failed, however, to produce any
lactone products when a water-insoluble 1-alkene was used.
(
ing in foodstuffs. The intense and characteristic odors of these
lactones are described as being “fruity” and in some cases as
“reminiscent of coconut” (γ-octalactone), “peach-like” (γ-deca-
and γ-dodecalactones), and “fatty” (γ-dodecalactone) (7). The
respective odor detection thresholds for γ-octa-, γ-deca-, and
γ-dodecalactone in water are 7, 11, and 7 ppb (2). To enhance
flavor, γ-lactones are added to many foodstuffs at concentrations
often comparable to those occurring naturally and within a range
of 0.01-60 ppm (7).
Accurate quantitation of flavor compounds is most readily
achieved through the addition of a known quantity of a stable
isotope labeled analogue to the sample as an internal standard
(SIDA) (8). Due to the nearly identical physical and chemical
properties of the labeled internal standard and the analyte, the
labeled and unlabeled materials are recovered with equal
efficiencies, and losses of the analyte during isolation and
measurement are compensated for. To minimize interferences
during GC-MS analysis, deuterium labeling should increase the
molecular weight of a labeled internal standard by at least 2
mass units. For γ-lactones, under standard electron impact GC-
MS conditions (70 eV), loss of the alkyl substituent at C4 is
favored, leading to an intense base peak at m/z 85 in the mass
Ring-deuterated γ-dodecalactone and γ-decalactone have been
reported by Haffner and Tressl (13) as metabolic products of
the yeast Soridiobolus salmonicolo. Ring-deuterated d4-oak
lactones have been prepared by Pollnitz et al. (14) by deuterium
exchange and borodeuteride reduction of 3-methyl-4-oxo-
octanoic acid. A similar strategy has been used to prepare d5-
γ- and δ-lactones with deuterium incorporated into both the
ring positions (C3 and C4) and the side chain (C5) (15, 16).
2
This paper reports the synthesis of [3,3,4- H3]- and [2,2,3,3-
2
H4]-ring-labeled γ-lactones using two general strategies: (1)
*
Author to whom correspondence should be addressed (telephone
00-64-6-356-8080; fax +00-64-6-351-7011; e-mail drowan@
hortresearch.co.nz).
hydrogenation of 4-hydroxypropargylic acids (17) with deute-
rium gas and (2) addition of carboxymethyl radicals to [1,1,2-
+
1
0.1021/jf048885b CCC: $27.50
© 2004 American Chemical Society
Published on Web 10/15/2004

7076 J. Agric. Food Chem., Vol. 52, No. 23, 2004
Hislop et al.
Scheme 1. Chemical Structures of
γ
-Dodeca- (1),
γ
-Deca- (2), and
diisopropylamine (4.12 mL, 31.4 mmol) in THF (20 mL) under argon
at 0 °C. This solution was added to a solution of propiolic acid (1.0 g,
γ
-Octalactones (3) and 6-Dodecyne-
γ-lactone (4) Showing Origin of
1
4.3 mmol) in THF (10 mL) at -78 °C. N,N,N′,N′-Tetramethylethyl-
the Base Peak m/z 85 in the Mass Spectrum
enediamine (5 mL) and heptanal (1.63 g, 14.3 mmol) were added, and
the mixture was warmed to room temperature with stirring. After 1 h,
water (10 mL), saturated NH
mL) were added, and the aqueous layer was washed with ether (3 ×
0 mL). The organic phase was evaporated, and the crude oil was
4
Cl (20 mL), and aqueous HCl (10%, 10
1
dissolved in ether (40 mL) and extracted with 2% NaOH (2 × 10 mL).
The aqueous phase was acidified with concentrated HCl (2 × 10 mL)
and re-extracted with ether (3 × 10 mL). The combined organic phases
were washed with water (2 × 10 mL) and brine (10 mL), dried over
4
MgSO , and concentrated in vacuo to give 4-hydroxydec-2-ynoic acid
as a white power (1.15 g, 44%). This was dissolved in ether (35 mL)
and treated with excess diazomethane (prepared from N-methyl-N-
nitrosotoluene-p-sulfonamide) at 0 °C for 5 min. Removal of volatiles
in vacuo and purification by flash chromatography on silica gel eluting
with hexane through to hexane/ethyl acetate (4:1) gave the title
compound (0.80 g, 28%) as a pale yellow oil: R
f
0.59 (hexane/ethyl
acetate 1:1); νmax (film) 3422, 2956, 2931, 2860, 1720, 1458, 1437,
-
1 1
1
254, 1049 cm ; H NMR δ 0.86 (3H, t, J ) 6.2 Hz, H10), 1.26 (6H,
s, H7 to H 9), 1.43 (2H, m, H6), 1.73 (2H, m, H5), 3.75 (3H, s, OCH ),
3
4
3
(
.46 (1H, t, J ) 6.6 Hz, H4); 13C NMR δ 14.0, 22.5, 24.9, 28.8, 31.6,
6.8, 52.8, 61.9, 75.9, 88.6, 163.8; MS, m/z (rel int %) 197 (52), 181
+
45), 113 (28), 69 (37), 55 (72), 43 (100). Found: M - H 197.1172,
C
11
H
17
O
3
requires 197.1178.
4
-tert-Butyldimethylsiloxydec-2-ynoic Acid Methyl Ester (5). To a
stirred solution of 4-hydroxydec-2-ynoic acid methyl ester (0.80 g, 4.0
mmol) in DMF (2 mL) at 0 °C was added imidazole (0.33 g, 4.9 mmol)
and tert-butyldimethylsilyl chloride (0.54 g, 5.0 mmol). The solution
was brought to room temperature and stirred for 18 h. Water (2 mL)
was added to the reaction, and the solution was partitioned against ether
(
(
3 × 25 mL). The combined organic extracts were washed with water
2 × 20 mL) and saturated brine (20 mL), dried over MgSO
4
,
concentrated in vacuo, and purified by flash chromatography on silica
gel. Eluting with hexane through to hexane/ethyl acetate (5:1) gave 5
(
0.84 g, 66%) as a colorless oil: R
f
0.59 (hexane/ethyl acetate 4:1);
-1
2H3]-1-alkenes (10-12) as well as a preliminary evaluation of
use of these compounds for SIDAs.
νmax (film) 2957, 2859, 1720, 1464, 1436, 1362, 1341, 1249, 1096 cm ;
1
H NMR δ 0.11 (3H, s, SiCH
H10 and C(CH ), 1.28 (6H, s, H7 to H9), 1.41 (2H, m, H6), 1.71
2H, m, H5), 3.76 (3H, s, OCH ), 4.44 (1H, t, J ) 6.4 Hz, H4); C
3 3
), 0.14 (3H, s, SiCH ), 0.89 (12H, s,
3 3
)
1
3
(
3
MATERIALS AND METHODS
NMR δ -5.1, -4.5, 14.1, 18.2, 22.6, 25.0, 25.7, 28.9, 31.7, 37.8, 52.6,
6
2.6, 75.6, 89.1, 153.8; MS, m/z (rel int %) 311 (2), 281 (7), 255 (52),
Chemicals. Reagents were obtained from the Aldrich Chemical Co.
Milwaukee, WI) and were used without further purification unless
otherwise stated. Reactions were performed under an atmosphere of
dry nitrogen in oven-dried glassware. Benzene, THF, and diethyl ether
2
29 (24), 203 (34), 171(33), 149 (7), 89 (100), 73 (49), 55 (21), 41
(
+
(19). Found: M - H 311.2043, C17
H O
31 3
Si requires 311.2042.
2
4
[2,2,3,3- H ]-4-tert-Butyldimethylsiloxydecanoic Acid Methyl Ester
(
BDH) were purified by distillation from sodium benzophenone ketyl.
6. To 5 (0.83 g, 2.7 mmol) dissolved in freshly distilled benzene (25
mL) was added Wilkinson’s catalyst (10 mol %, 0.125 g). The flask
was fitted to a hydrogenation apparatus and degassed three times before
Reactions were monitored by thin-layer chromatography on aluminum-
backed Kieselgel 60 F254 silica gel plates (Merck) with the specified
solvents. Compounds were visualized under an ultraviolet lamp followed
by treatment with alkaline potassium permanganate and strong heating.
Flash column chromatography was carried out using silica gel (60-62
µm, Merck). Short path distillation was carried out using a GKR-51
Kugelrohr (B u¨ chi).
stirring vigorously while the uptake of D
monitored. After consumption of 2.0 equiv of D
2
gas (99.8% atom D) was
(60 h), the flask was
2
isolated from the reservoir of deuterium gas. Benzene was removed
under reduced pressure and the crude oil filtered through a small plug
of Celite with hexane/ethyl acetate (20:1). The product was purified
further by flash chromatography on silica gel eluting with hexane
through to hexane/ethyl acetate (20:1) to give 6 (0.83 g, 97%) as a
1H and 13C nuclear magnetic resonance (NMR) spectra were recorded
in CDCl
3
on a JEOL HNM-GX270W NMR spectrometer. Chemical
shifts (δ) are in parts per million relative to chloroform at 7.27 ppm
colorless oil: R
2858, 1743, 1463, 1435, 1361, 1256, 1198, 1091 cm ; H NMR δ
0.04 (6H, s, Si(CH ) 0.88 (12H, s, H10 and C(CH ), 1.27 (8H, br
s, H6 to H9), 1.43 (2H, m, H5), 3.66 (3H, s, OCH
f
0.56 (hexane/ethyl acetate 4:1); νmax (film) 2956, 2931,
1
13
-1
1
for H (270 MHz) and at 77.0 ppm for C (67.8 MHz). The following
abbreviations are used: s, singlet; d, doublet; t, triplet; m, multiplet;
br, broad. Infrared spectra were measured on a Paragon 1000 FT-IR
spectrometer as thin films between NaCl plates. Capillary gas chro-
matography-mass spectrometry (GC-MS) was carried out on a VG70-
3
)
2
3 3
)
1
3
3
); C NMR δ -4.6,
-4.4, 14.1, 18.1, 22.6, 25.2, 25.9, 29.5, 31.9, 37.0, 51.4, 71.0, 174.4;
MS, m/z (rel int %) 320 (<1), 289 (10), 263 (100), 230 (76), 174 (13),
2
50S magnetic sector instrument operating at a 70 eV ionization
161 (7), 132 (7), 115 (15), 101 (9), 89 (76), 73 (89), 59 (44), 41 (27).
+
potential (spectral interface at 180 °C) coupled to a Hewlett-Packard
Found: M 320.2688, C17
H
32
D
4
O
3
Si requires 320.2688.
2
5
890 series II gas chromatograph fitted with a 30 m × 0.25 mm i.d.
[2,2,3,3- H
4
]-γ-Decalactone. To a stirred solution of 6 (0.73 g, 2.9
DB1 column, film thickness ) 0.25 µm; temperature was programmed
from 40 °C (5 min) to 280° C at 5 °C/min (hold for 20 min), helium
mmol) in THF (40 mL) was added concentrated HCl (1 mL). After 2
h of stirring, the reaction was diluted with ether (10 mL) and partitioned
against saturated sodium bicarbonate (2 × 20 mL), water (2 × 20 mL),
head pressure ) 5 psi.
Synthesis of [2,2,3,3- H
2
4
]-γ-Lactones. 4-Hydroxydec-2-ynoic Acid
4
and saturated brine (20 mL). The solution was dried over MgSO and
Methyl Ester. A solution of lithium diisopropylamide was prepared by
stirring n-butyllithium (1.45 M [hexanes], 21.7 mL, 31.4 mmol) and
concentrated in vacuo to give a pale oil. Flash chromatography on silica
gel eluting with hexane/ethyl acetate (4:1) gave an oil that was further

Synthesis of Deuterated
γ-Lactones
J. Agric. Food Chem., Vol. 52, No. 23, 2004 7077
purified by distillation (120 °C at 0.2 mmHg) to the title compound
0.365 g, 92%) as a colorless oil: R 0.29 (hexane/ethyl acetate 4:1);
max (film) 3524, 2931, 2859, 2361, 1770, 1467, 1379, 1348, 1202,
(9), 100 (5), 85 (100), 70 (4), 55 (10), 43 (9), 41 (13). Found: M+
(
ν
f
170.1300, C10
H
18
O
2
requires 170.1307.
2
Synthesis of [3,3,4- H ]-γ-Dodecalactone. 2-Iodoacetamide (0.215
3
-
1 1
1
112, 1062, 1112, 1062, 1012 cm ; H NMR δ 0.88 (3H, t, J ) 6.4
g, 1.2 mmol) and ACCN (0.557 g, 2.3 mmol) were added to a stirred
2
3
Hz, H10) 1.27 (8H, br s, H6 to H9), 1.60 (1H, m, H5), 1.71 (1H, m,
solution of [1,1,2- H ]-1-decene (0.498 g, 3.5 mmol) in benzene (23
1
3
H5), 4.47 (1H, t, J ) 6.4 Hz, H4); C NMR δ 14.1 (q), 22.6 (t), 27.9
m, CD ), 28.6 (m, CD ) 25.2 (t), 29.0 (t), 31.7 (t), 35.6 (t), 80.9 (d),
mL). Water (2.15 mL, 0.1 mol) was added, and the mixture was refluxed
under nitrogen for 18 h. Aqueous HCl (10%, 2.5 mL) and water (2.5
mL) were added, and the mixture was extracted with ether (3 × 20
mL). The combined organic extracts were washed with water (2 × 20
(
2
2
1
77.2 (s); MS, m/z (rel int %) 174 (<1), 156 (1), 141 (4), 132 (8), 104
(4), 89 (100), 88 (51), 70 (7), 60 (7), 56 (8), 55 (9), 43 (15), 41 (17).
+
Found: M 174.1559, C10
H
14
D
4
O
2
requires 174.1557.
mL) and saturated brine (20 mL), dried over MgSO , and concentrated
4
2
[
2,2,3,3- H
4
]-γ-Dodecalactone was prepared from nonanal as above.
in vacuo. The crude oil was purified by flash chromatography on silica
Flash chromatography on silica gel and distillation (140 ° C at 0.2
mmHg) gave the title compound (52 mg, 17% overall) as a colorless
gel, eluting with hexane through to hexane/ethyl acetate (4:1), to give
2
3
recovered [1,1,2- H ]-1-decene (17%) and ACCN (79%). Further elution
oil: R
f
0.29 (hexane/ethyl acetate 4:1); νmax (film) 3519, 2927, 2856,
gave a colorless oil, which was further purified by short path distillation
(135-140 °C at 0.2 mmHg) to give the title compound (0.163 g, 23%)
f
at 96% deuterium incorporation: R 0.45 (hexane/ethyl acetate 4:1);
-
1
1
1
0
770, 1467, 1378, 1348, 1203, 1161, 1113, 1060 cm ; H NMR δ
.88 (3H, t, J ) 6.4 Hz, H10), 1.27 (12H, br s, H6 to H11), 1.60 (1H,
13
m, H5), 1.71 (1H, m, H5), 4.47 (1H, t, J ) 6.4 Hz, H4); C NMR δ
4.2 (q), 22.7 (t), 25.3 (t), 27.5 (m, CD ), 28.7 (m, CD ), 29.2 (t), 29.4
t), 29.5 (t), 31.9 (t), 35.6 (t), 80.9 (d), 177.1 (s); MS, m/z (rel int %)
41 (2), 132 (5), 104 (4), 89 (100), 88 (11), 70 (7), 69 (7), 60 (5), 56
11), 55 (12), 43 (15), 41 (21). Found: M+ 202.1868, C12
νmax (film) 3525, 2927, 2856, 1778, 1467, 1424, 1378, 1259, 1228,
-
1
1
1
(
1
(
2
2
1187, 1124, 1010 cm ; H NMR δ 0.88 (3H, t, J ) 6.2 Hz, H12),
1.27 (11H, br s, H5 and H7 to H11), 1.46 (1H, m, H6), 1.58 (1H, m,
H6), 1.73 (1H, m, H5), 2.50 (2H, s, H2), 4.47 (0.04H, m, residual H-);
13
H
18
D
4
O
2
C NMR δ 14.1 (q), 22.6, 25.2, 27.4 (m, C3), 28.7, 29.2, 29.3, 29.4,
requires 202.1871.
31.8, 35.4, 80.4 (t, C4), 177.1; MS, m/z (rel int %) 201 (0.2), 183 (0.9),
2
4
[2,2,3,3- H ]-γ-Octalactone was prepared from pentanal as above.
141 (3), 131 (7), 103 (6), 98 (5), 88 (100), 87 (18), 84 (5), 70 (10), 69
+
Flash chromatography and distillation (110 °C at 2 mmHg) gave the
title compound (0.36 g, 27% overall) as a colorless oil: R 0.29 (hexane/
ethyl acetate 4:1); νmax (film) 3520, 2958, 2934, 2863, 1772, 1467,
(8), 60 (4), 56 (13), 55 (12), 43 (16), 41 (20). Found: M 201.1804,
C
12
H
19
D
3
O
2
requires 201.1808.
f
2
Synthesis of [3,3,4- H
3
]-γ-Dodecalactone (10). To a stirred solution
-
1
1
2
2
1
)
380, 1348, 1202, 1108, 1061, 1009 cm ; H NMR δ 0.88 (3H, t, J
6.4 Hz, H8), 1.27 (4H, br s, H6, 7) 1.60 (1H, m, H5), 1.71 (1H, m,
3
of [1,1,2- H ]-1-decene (0.113 g, 0.79 mmol, 93% H) and acetic acid
(10 mL) was added manganic acetate dihydrate (0.57 g, 2.1 mmol)
and potassium acetate (3.56 g). The solution was refluxed for 1.5 h
until the brown color had disappeared, and the reaction mixture was
diluted with water (5 mL) and extracted with ether (3 × 15 mL). The
1
3
H5), 4.47 (1H, t, J ) 6.4 Hz, H4); C NMR δ 13.8 (q), 22.3 (t), 27.2
t), 28.0 (m, CD ), 28.8 (m, CD ), 35.1 (t), 80.7 (d), 177.0 (s); MS,
(
2
2
m/z (rel int %) 146 (<1), 125 (1), 104 (4), 90 (4), 89 (100), 88 (35),
+
6
0 (6), 41 (8). Found: M 146.1246, C
8
H
10
D
4
O
2
requires 146.1245.
4
organic extracts were combined, dried over MgSO , and concentrated
Optimization Procedure for the Synthesis of γ-Decalactone 2.
in vacuo. The resulting crude material was passed through a short plug
of silica gel with pentane (10 mL) and ethyl acetate (10 mL) to yield
a pale yellow oil, which was further purified by short path distillation
(136-140 °C at 0.2 mmHg) to give the title compound (0.11 g, 69%):
Typically, 1-octene (0.168 g, 1.50 mmol) was added to a glass
scintillation vial containing a solution of 2-iodoacetamide or 2-iodoace-
tic acid (0.5 mmol) and radical initiator (1.0 mmol) in benzene (10
mL). The vial was flushed with argon, sealed (screw-cap lid and
Parafilm), and marked to indicate the initial volume. A blank of benzene
1
H NMR δ 4.46 (0.10H, m, residual H4) indicated 90% deuteration.
2
Synthesis of [3,3,4- H
3
]-γ-Octalactone. 2-Iodoacetamide (0.13 g, 0.7
(
10 mL) was also prepared for each run. Mole ratios were generally
mmol) and ACCN (0.339 g, 1.4 mmol) were added to a stirred solution
of [1,1,2- H ]-1-hexene (0.183 g, containing some [1- H ]-1-hexyne)
3 1
2
2
varied by factors of 2. The vials were placed in a vibrating water bath
(
200 rpm) at 75 °C. After 18 h, aqueous HCl (10%, 1 mL) and water
in benzene (14 mL). Water (1.26 g, 70 mmol) was added, and the
mixture was refluxed under nitrogen for 18 h. Aqueous HCl (10%, 2.5
mL) and water (2.5 mL) were added, and the mixture was extracted
with ether (3 × 10 mL). The combined organic extracts were washed
(1 mL) were added to each vial. For GC analysis, 1 mL of the crude
reaction mixture was diluted to 10 mL with ether. The blank (benzene
only) was likewise diluted and spiked with γ-decalactone (1 µL).
Product analysis was carried out on a Hewlett-Packard model 5890
series II gas chromatograph equipped with a flame ionization detector.
Separations were achieved using a 30 m × 0.25 mm i.d. SE-30 Econo-
Cap capillary column with a film thickness of 0.25 µm; the temperature
was programmed from 50 °C (1 min) at 10 °C/min to 240 °C (5 min);
the injector temperature was 200 °C, and the detector temperature was
with water (2 × 10 mL) and brine (10 mL), dried over MgSO
4
, and
concentrated in vacuo. The resulting material was purified by flash
chromatography on silica gel, eluting with hexane through to hexane/
ethyl acetate (4:1) to give the title compound (0.017 g, 6%) as a pale
f
oil with 92% deuterium incorporation: R 0.21 (hexane/ethyl acetate
1
6:1); H NMR δ 0.92 (3H, t, J ) 6.4 Hz, H8), 1.39 (3H, m, H7 and
H5), 1.43 (1H, m, H-6), 1.74 (1H, m, H5), 2.52 (2H, s, H2), 4.46
(0.08H, m, residual H4); 13C NMR δ 13.9, 22.5, 27.3 (m, C3), 28.7,
28.8, 35.1, 80.5 (t, C4), 177.0; MS, m/z (rel int %) 145 (0.8), 144 (0.6),
2
50 °C. The column head pressure was 10 psi of hydrogen. The best
results from each set of experiments were repeated and used as initial
values in further optimization experiments.
Synthesis of γ-Decalactone 2. 1-Octene (0.168 g, 1.50 mmol) and
water (0.90 mL, 50 mmol) were added to a stirred solution of
127 (1), 126 (2), 103 (7), 102 (4), 88 (100), 87 (79), 86 (15), 85 (5),
+
71 (5), 57 (7), 41 (7). Found: M 145.1178, C
145.1167.
Synthesis of [1,1,2- H ]-1-Alkenes. [1- H ]-1-Decyne. To a stirred
3 1
8 11 3 2
H D O requires
2
-iodoacetamide (0.093 g, 0.503 mmol) and ACCN (0.242 g, 0.992
2
2
mmol) in benzene (10 mL). This mixture was refluxed under argon
for 18 h, whereupon water (1 mL) and aqueous HCl (10%, 1 mL) were
added. The reaction mixture was extracted with ether (3 × 5 mL), and
the combined organic extracts were washed with water (2 × 5 mL)
solution of 1-decyne (1.53 g, 11.1 mmol) in THF (40 mL) at -78 °C
was added n-butyllithium (1.2 M [hexanes], 10.8 mL, 13.3 mmol). After
10 min of stirring, D O (0.24 mL, 13 mmol, 99.9% atom D) was added.
2
The reaction mixture was warmed to room temperature, stirred (2 h),
and washed with ether (3 × 20 mL) and aqueous HCl (10%, 10 mL).
The organic phase was washed with water (3 × 10 mL) and saturated
brine (10 mL), and the aqueous fractions were back-extracted with ether
and saturated brine (5 mL), dried over MgSO
4
, and concentrated in
vacuo. Flash chromatography on silica gel, eluting with hexane through
to hexane/ethyl acetate (4:1), gave the title compound as an oil, which
was further purified by short path distillation (112-116 °C at 0.2
mmHg) (0.083 g, 32% based on 1-octene): R
f
) 0.31 (hexane/ethyl
(2 × 10 mL). The combined organic fractions were dried over MgSO
4
acetate 4:1); νmax (film) 2955, 2931, 2870, 1775, 1467, 1420, 1363,
and concentrated in vacuo to give the title compound (1.50 g, 97%)
with 98% deuterium incorporation as a pale oil: νmax (film) 2927, 2857,
2598, 1467, 1378, 1327, 1116 cm 1; 1H NMR δ 0.88 (3H, t, J ) 6.2
Hz, H10) 1.28 (8H, br s, H6 to H9), 1.40 (2H, m, H5), 1.51 (2H, quintet,
J ) 6.8 Hz, H4), 1.92 (0.02H, t, residual H1), 2.18 (2H, t, J 6.8 Hz,
H3); 13C NMR δ 14.2, 18.4, 22.7, 28.6, 28.8, 29.1, 29.2, 31.9, 67.9 (t,
-
1
1
1
282, 1182, 1063, 1012 cm ; H NMR δ 0.82 (3H, t, J ) 6.4 Hz,
-
H10), 1.23 (7H, br s, H5 and H7 to H9), 1.37 (1H, m, H6), 1.58 (1H,
m, H6), 1.68 (1H, m, H5), 1.82 (1H, m, H3), 2.27 (1H, m, H3), 2.47
1
3
(
2H, m, H2), 4.42 (1H, m, H4); C NMR δ 14.1, 22.6, 25.2, 28.0,
2
8.9, 29.0, 31.7, 35.6, 81.0, 177.1; MS, m/z (rel int %) 170 (<1), 128

7078 J. Agric. Food Chem., Vol. 52, No. 23, 2004
Hislop et al.
2
Scheme 2. Synthesis of [2,2,3,3- H
4
]-
γ
4
-Decalactone (2-d ) by Alkylation of Propiolic Acid with Heptanal
Cl), 84.2 (t, C2); MS, m/z (rel int %) 139 (<1), 110 (6), 96 (31), 82
(100 mL) under argon and sonicated for 30 min. The mixture was
4
quenched at 0 °C with D O (3.41 g, 0.17 mol) in the presence of d -
+
(
90), 68 (51), 57 (49), 55 (100), 43 (66), 41 (99). Found: M 139.1475,
2
C
10
H
17D requires 139.1471.
acetic acid (1.95 mL, 34 mmol). The reaction mixture was washed
sequentially with 10% HCl (20 mL), water (2 × 20 mL), and brine
(20 mL). The combined aqueous fractions were back-extracted with
2
[1,1,2- H
3
]-1-Decene. Lindlar’s catalyst (0.33 g) and quinoline (0.25
2
mL) were added to a stirred solution of [1- H
1
]-1-decyne (1.50 g, 108
mmol) in pentane (40 mL). The reaction flask was flushed three times
with deuterium gas (∼10 mL, 99.8% atom D) and attached to a
hydrogenation apparatus, where the solution was stirred vigorously
while D uptake was monitored. After 18 h, deuterium uptake was
2
complete, and the mixture was filtered through a short plug of Celite
diethyl ether (2 × 20 mL). The organic fractions were combined, dried
2
(MgSO
4
), and evaporated to give [1- H
1
]-1-octyne (87% deuteration).
2
Synthesis of [1,1,2- H
tetradecane (50 mL) was stirred with prewashed NaH (1.10 g, 46 mmol)
for 2 h at 0 °C. The reaction was quenched with D O (0.95 mL, 48
3
]-1-Hexene. 1-Hexyne (3.60 g, 44 mmol) in
2
and rinsed with ether (2 × 20 mL), then washed with aqueous HCl
mmol) and stirred for 2 h. Lindlar’s catalyst (1.32 g) and quinoline
(1.0 mL) were added, and the flask was swept with deuterium gas (2
× ∼15 mL) prior to reduction with deuterium gas. Additional catalyst
(150 mg) was added after 1 week. Deuterium uptake ceased after 2
weeks when the required volume was consumed. The reaction mixture
(
10%, 20 mL), saturated sodium bicarbonate (2 × 10 mL), water (2 ×
1
0 mL), and saturated brine (10 mL). The combined organic phases
were dried over MgSO and concentrated in vacuo to give a yellow
4
oil. Short path distillation (76-80 °C at 15 mmHg) gave the title
compound (0.944 g, 61%) as a colorless oil with 93% deuterium
incorporation: νmax (film) 2958, 2926, 2855, 1584, 1467, 1378, 1118
4
was filtered through a short column of MgSO and distilled. A fraction
1
(bp 72-80 °C, 42% yield) was shown by H NMR to consist of a
-
1
1
2
2
cm ; H NMR 0.92 (3H, t, J ) 6.2 Hz, H10) 1.31 (12H, br s, H4 to
H9), 2.07 (2H, t, J ) 6.2 Hz, H3), 4.90-4.95 (0.07H, m, residual H1),
mixture of [1,1,2- H
3
]-1-hexene and [1- H
1
]-1-hexyne in a ratio of 1.0:
2
]-1-hexene: 1H NMR δ 0.90 (3H, t, J 7.2 Hz, H6),
0.8. For [1,1,2- H
3
1
3
5
.42 (0.035H, m, residual H2); C NMR 14.2, 22.8, 29.0, 29.3, 29.4,
1.36 (4H, m, H4, 5), 2.03 (2H, m, H3), 4.92-4.96 (0.06H, m, residual
2
9.6, 32.0, 33.7, 113.6 (m, C1), 138.9 (t, C2); MS, m/z (rel int %) 143
H1), 5.42 (0.03H, m, residual H2); 13C NMR δ 13.9, 22.2, 31.1, 33.3,
(
15), 114 (7), 100 (14), 98 (12), 86 (22), 83 (20), 76 (75), 56 (100), 43
113.5 (m, C1), 131.2 (t, C2); GC-MS, m/z (rel int %) 87 (27), 74 (13),
+
+
(91), 41 (59). Found: M 143.1753, C10
H
17
D
3
requires 143.1753.
70 (14), 57 (88), 43 (91), 41 (100). M 87.1127 C
6
H
9
D
3
requires
2
2
1
Synthesis of [1- H
1
]-1-Octyne. To a stirred solution of 1-octyne (3.75
1
87.1127. For [1- H ]-1-hexyne: H NMR δ 1.56 (1.6H, m, H3), other
g, 34 mmol) in THF (100 mL) at -78 °C was added n-butyllithium
signals obscured; 13C NMR δ 13.8, 19.0, 22.3, 31.3, 68.2 (m, C2),
(2.0 M [hexanes], 20 mL, 40 mmol). After 10 min of stirring, D
2
O
84.3 (m, C1).
(0.83 mL, 40 mmol, 99.9% atom D) was added. The reaction mixture
was warmed to room temperature and stirred (2 h) with ether (40 mL)
and aqueous HCl (10%, 20 mL). The organic phase was washed with
water (3 × 20 mL) and saturated brine (20 mL), and the aqueous
fractions were back-extracted with ether (2 × 10 mL). The combined
RESULTS AND DISCUSSION
Two approaches to the synthesis of ring-deuterated γ-lactones
were evaluated: first, the synthesis of [2,2,3,3- H4] ring-
2
organic fractions were dried over MgSO
4
and concentrated in vacuo
deuterated γ-lactones by the reduction of a 4-hydroxypropargylic
acid (17) with deuterium gas and, second, the synthesis of [3,3,4-
to give the title compound (3.28 g, 87%). Attempted purification by
2
distillation gave a mixture (bp 81-86 °C at 16 mmHg) of [1- H
1
]-1-
2
H3] ring-deuterated compounds by the addition of a carboxy-
octyne (92% deuterium incorporation) and 1-butanol (ca. 1:1). For
2
methyl radical to a [1,1,2- H3]-1-alkene (10-12).
2
1
[
1- H
1
]-1-octyne: H NMR δ 0.88 (3H, t, J ) 6.2 Hz, H8), 1.29 (6H,
2
[
2,2,3,3- H4]-γ-Lactones by Reduction of 4-Hydroxypro-
br s, H5, 6, and 7), 1.51 (2H, quintet, H4), 1.93 (0.08H, t, J ) 6.8 Hz,
2
pargylic Acids with Deuterium Gas. The [2,2,3,3- H4]-γ-
octa-, deca-, and dodecalactones were synthesized by adaptation
of the reaction schemes reported by Midland and Tramontano
1
3
residual H1), 2.16 (2H, t, J ) 7.0 Hz, H3); C NMR δ 14.0, 18.4,
2
(
2.6, 28.5, 31.3, 67.8, 84.2 (t, C-1); MS, m/z (rel int %) 111 (2), 96
+
16), 82 (99), 68 (41), 55 (60), 43 (100), 41 (77). Found: M 111.1147,
(17) and Herrman et al. (18) (Scheme 2). Thus, alkylation of
8
C H13D requires 139.1158.
2
Synthesis of [1- H
1
]-1-Octyne (Sodium Hydride). 1-Octyne (3.75 g,
the dianion of propiolic acid with heptanal gave 4-hydroxydec-
2-ynoic acid in 44% yield. A homogeneous hydrogenation
34.0 mmol) was added to ether-washed NaH (2.64 g, 0.11 mol) in ether

Synthesis of Deuterated
γ-Lactones
J. Agric. Food Chem., Vol. 52, No. 23, 2004 7079
Figure 2. Mass spectra (GC-MS, 70 eV) of (A)
γ-decalactone and (B)
2
[
2,2,3,3- H
4
]-
γ
-decalactone.
Figure 1. Mass spectra (GC-MS, 70 eV) of (A)
γ
-dodecalactone, (B)
2
2
[
3
3,3,4- H ]-γ
-dodecalactone, and (C) [2,2,3,3- H
4
]-
γ
-dodecalactone.
catalyst [Wilkinson’s, RhCl(PPh3)3] was chosen to prevent
scrambling of the deuterium label (19); however, a trial reaction
involving the reduction with hydrogen of 4-hydroxydodec-2-
ynoic acid proceeded very slowly and in poor yield (6 weeks
and 24% yield, respectively). 4-Hydroxydec-2-ynoic acid was
therefore protected as the methyl ester tert-butyldimethsilyl ether
5
(43% yield over two steps). Reduction with deuterium gas
and Wilkinson’s catalyst in benzene then gave the deuterated
derivative 6 in 97% yield after 60 h. Deprotection with catalytic
2
HCl in THF gave [2,2,3,3- H4]-γ-decalactone (2-d4) in 92%
yield after distillation (17% overall yield). Incorporation of
deuterium at C2 and C3 was shown by the nearly complete
absence of signals at δ 2.34 and 2.18 (H2 and H3, respectively)
and the collapse of a multiplet (δ 4.40, H4) into a triplet in the
1
H NMR. Integration of residual signals indicated 89% incor-
poration of deuterium.
Analogous procedures were used to synthesize [2,2,3,3- H4]-
2
Figure 3. Mass spectra (GC-MS, 70 eV) of (A)
γ
-octalactone, (B) [3,3,4-
2H
γ
-octalactone, and (C) [2,2,3,3- H
2
-octalactone.
3
]-
4
]-γ
γ-dodecalactone (19% overall yield, 97% deuterium incorpora-
1
2
tion by H NMR) and [2,2,3,3- H4]-γ-octalactone (27% overall
yield, 90% deuterium incorporation).
from C2 was occurring in the GC injector port through
enolization of the deuterium R to the lactone carbonyl, possibly
with residual water in the samples. Although the extent of this
loss was reproducible throughout a series of GC-MS samples,
and could be corrected for in SIDA, it provided the impetus to
develop an improved synthesis of labeled γ-lactones.
GC-MS analysis gave mass spectra (Figures 1-3) with a
base peak at m/z 89, 4 mass units higher than in the unlabeled
compound and corresponding to the incorporation of four
deuterium atoms. The mass spectra of some samples (e.g.,
Figures 2 and 3) also included a major peak at m/z 88, indicating
the presence of significant amounts of a trideuterated species,
2
[3,3,4- H3]-γ-Lactones by Carboxymethyl Radical Addi-
1
2
inconsistent with the results of H NMR analysis. The molecular
tion to [1,1,2- H3]-1-Alkenes. The method of Yorimitsu et al.
ion (<1%) appeared as a cluster (201:202:203:204 ) 39:68:
(12) for the synthesis, in water, of ω-hydroxyalkyl-γ-lactones
was adapted (Scheme 3) and optimized for the synthesis of
water-insoluble γ-lactones. The introduction of deuterium into
the ring of the γ-lactone requires the availability of the
1
00:70) centered at m/z 203, confirming some loss of label;
however, similar multiple ions were observed for both deuterated
and nondeuterated γ-lactones. Attempted CI-GC-MS of deu-
terated and nondeuterated samples gave similar molecular ion
clusters. On the basis of varying ion ratios (m/z 89:m/z 88)
between samples, it was concluded that partial loss of deuterium
2
corresponding [1,1,2- H3]-1-alkenes. Sirokman et al. (20) have
2
reported the synthesis of [1- H1]-1-alkynes with high isotopic
purity by the quenching of the corresponding sodium acetylide

7080 J. Agric. Food Chem., Vol. 52, No. 23, 2004
Hislop et al.
2
Scheme 3. Synthesis of [3,3,4- H
3
]-γ
3
-Dodecalactone (1-d ) from 1-Decyne
Scheme 4. Mechanism Proposed (12) for the Free Radical Addition of 2-Iodoacetamide to 1-Alkenes To Give
γ-Lactones
with deuterium oxide. Reduction of the deuterated acetylene
with gaseous deuterium in the presence of Lindlar’s catalyst
would then afford the required [1,1,2- H3]-1-alkenes (Scheme
out with 1-octene using either 2-iodoacetamide or 2-iodoacetic
acid, initially in small glass vials and later in conventional
glassware. The reaction conditions of Yorimitsu et al. (12) with
olefin, 2-iodocarbonyl, and radical initiator in a 1.5:1.0:0.5 mole
ratio were chosen as a starting point. Initial results indicated
ACCN 7 gave marginally higher yields (∼3%) than either 4,4′-
azobis(4-cyanopentanoic acid) or 2,2′-azobis(isobutyronitrile)
(0-3%), and further optimization used only this compound. Two
cycles of optimization identified the combination of 1-octene
(1.5 mmol), 2-iodoacetamide (0.5 mmol), and ACCN (1.0
mmol) as giving a 24% GC yield of γ-decalactone 2. The
proposed mechanism (12) requires water to hydrolyze the imino-
ether intermediate 11. The significance of extraneous water was
realized when a 22% isolated (24% GC yield) yield of
γ-decalactone obtained above from a reaction in a scintillation
vial gave no γ-lactone in a round-bottom flask under similar
“anhydrous” conditions. A final optimization was carried out
under nitrogen in conventional round-bottom flasks (20 mL)
(Table 1). A 28% GC yield was obtained with 50 equiv of water
2
3
).
The formation of γ-lactones by free radical addition to
1
4
1
-alkenes is the result of a complex series of reactions (Scheme
) initiated by the thermal decomposition of the radical initiator
,1′-azo-bis(cyclohexanecarbonitrile) (7, ACCN) to generate two
equivalent cyclohexyl radicals 8. In a second step, the cyclohexyl
radical 8 abstracts an iodine atom from a 2-iodocarbonyl species
to give an acetamide radical. The acetamide radical adds to the
1
-alkene to produce the secondary carbon-centered radical 9,
to which iodine is transferred either from a second molecule of
-iodoacetamide or from iodocyclohexylnitrile formed initially
2
in the iodine abstraction step. Cyclization of 10 under the
reaction conditions, with loss of HI, gives the imino-ether 11
(12), which is hydrolyzed to give the γ-lactone product. Initially
this reaction, when run in benzene, produced no γ-lactone
products. Optimization of the reaction condition was carried

Synthesis of Deuterated
γ-Lactones
J. Agric. Food Chem., Vol. 52, No. 23, 2004 7081
and 2.26 ppm (H3). The two-proton multiplet (H2) at 2.52 ppm
had collapsed into a broadened singlet of comparable chemical
Table 1. Effect of Concentration of Water on GC Yield of
-Decalactone (2) Produced from Reaction of 2-Iodoacetamide with
-Octene
γ
1
1
3
shift (2.52 ppm). The C NMR signals for the deuterated
carbons were easily distinguishable, with C4 appearing as a 1:1:1
triplet at 80.8 ppm and C3 as a multiplet centered around 27.4
ppm. A molecular ion of m/z 201 (<1%) was obtained by GC-
MS analysis of the distilled material, 3 mass units above that
of γ-dodecalactone. The expected base peak of m/z 88 was
observed (Figure 1B).
1
(
-octene
mmol)
2-iodoacetamide
(mmol)
ACCN
(mmol)
water
(mmol)
yield of γ-
decalactone (2) (%)
a
1.5
1.5
1.5
1.5
0.5
0.5
0.5
0.5
1.0
1.0
1.0
1.0
5.0
10.0
50.0
3
12
28
14
100.0
2
Attempted Synthesis of [3,3,4- H3]-γ-Decalactone. Treat-
a
Based on 1-octene.
ment of 1-octyne with 1.2 equiv each of n-butyllithium and then
2
D2O gave an 87% yield of crude [1- H1]-1-octyne contaminated
Table 2. Isolated Yields (Based on 1-Alkene) of Deuterated and
Nondeuterated -Lactones Obtained by Addition of Iodoacetamide and
Mn(OAc) -Derived Acetoxy Radicals to Appropriate 1-Alkene
with residual hexanes. Attempts to purify this product resulted
in further significant losses (80-90%), so the crude product
was hydrogenated directly with deuterium gas using Lindlar’s
catalyst and quinoline in pentane to give a 61% yield after
γ
3
Precursors
2
distillation of [1,1,2- H3]-1-octene with 88% deuterium incor-
yield % of
1
2
poration by H NMR. This product was contaminated with
product
lactone
yield % of
[3,3,4- H
γ
3
]-
reagents
γ
-lactone
-lactone
significant quantities of 1-butanol (∼40%), presumably from
reaction of the n-butyllithium reagent with atmospheric oxygen.
All attempts to use this product in the preparation of [3,3,4-
γ
γ
-octa-
-deca-
2-iodoacetamide/ACCN
2-iodoacetamide/ACCN
32
33
38
32
6
0
a
2
2
Mn(OAc)
2-iodoacetamide/ACCN
Mn(OAc) /HOAc
2-iodoacetamide/ACCN
Mn(OAc) /HOAc
3
/HOAc
H3]-γ-decalactone were unsuccessful. Alternatively, [1- H1]-
-octyne was prepared by reaction of 1-octyne with sodium
hydride and quenching with D2O/acetic acid-d4, but at best an
7% incorporation of deuterium was achieved. Although disap-
γ
-dodeca-
23
69
1
3
5.2b
40
6-dodecyno-γ-
8
3
pointing, unlabeled γ-decalactone was isolated in 33% yield
a
2
]-1-octene, contaminated with n-butanol. b Olefin
by this procedure, suggesting that the target compound would
Olefin precursor, [1,1,2- H
3
2
precursor, 1-decen-4-yne. Yield excludes recovered starting material (40%).
be accessible by this reaction given access to pure [1,1,2- H3]-
1
-octene.
2
under a nitrogen atmosphere. When repeated preparatively,
γ-decalactone was isolated in 28% yield after distillation.
Comparable yields of γ-octa- and γ-dodecalactone (32%) were
also obtained under these conditions (Table 2).
Synthesis of [3,3,4- H3]-γ-Octalactone. Due to the volatility
2
of reagents and products, the synthesis of [1,1,2- H3]-1-hexene
required a different approach, and the direct transformation from
1-hexyne (bp 64 °C) with recovery by distillation from high
boiling solvents was investigated. 1-Hexyne in tetradecane was
treated sequentially with 1.05 equiv each of sodium hydride
and D2O followed by hydrogenation in situ with Lindlar’s
catalyst and deuterium gas. Distillation gave a 42% yield of a
2
Synthesis of [3,3,4- H3]-γ-Dodecalactone. Deprotonation of
1
-decyne with n-BuLi in THF at -78 °C and quenching of the
2
reaction mixture with deuterium oxide gave [1- H1]-1-decyne
in 97% isolated yield after distillation. Integration of the residual
1
2
signal in the H NMR at 1.94 ppm (alkynic proton, 0.02 H)
mixture (1:0.8) of [1,1,2- H3]-1-hexene (with 94% deuterium
incorporation) and [1- H1]-1-hexyne. To test if residual 1-hexyne
2
indicated 98% deuterium incorporation. In addition, the two-
proton triplet of doublets for H3 had collapsed to a simple triplet
at 2.18 ppm. The C NMR spectra showed the terminal alkynic
signals (C1 and C2) much reduced and replaced by a pair of
would interfere with γ-lactone synthesis, 1-hexyne was substi-
tuted for the 1-alkene under otherwise identical reaction
conditions. The only product isolated from the reaction was
identified by NMR as a 6:1 cis/trans mixture of 4-iodo-3-
13
1:1:1 triplets. GC-MS confirmed the deuteration with a molec-
1
ular ion of m/z 139, 1 mass unit higher than for 1-decyne.
Hydrogenation of 12 with deuterium gas in the presence of
Lindlar’s catalyst poisoned with quinoline gave 13 in 61% yield
octenamide (14%). Significant in the H NMR was the appear-
ance of two doublets H2 (3.00 and 3.12 ppm) in a ratio of 6:1
13
and a single proton triplet H3 (5.79 ppm). The C NMR showed
amide (172.3 and 174.5 ppm) and alkenic carbons [94.6 and
1
after distillation. The H NMR showed the nearly complete
98.7 (C4), and 114.6 and 116.4 (C3) ppm]. This result suggested
absence of the alkenic protons, corresponding to 93% deuterium
incorporation. The two-proton multiplet (H3) of 1-decene had
that the lactonization reaction should proceed in the presence
of residual 1-hexyne.
collapsed into a triplet at 2.07 ppm. 1 C NMR data showed a
reduced intensity for the deuterated signals with splitting of the
two alkenic signals into a multiplet at 113.6 ppm (C1) and a
3
2
2
Reaction of [1,1,2- H ]-1-hexene (contaminated with [1- H ]-
3
1
1-hexyne) with 2-iodoacetamide under optimized conditions
2
3
1
:1:1 triplet at 138.9 ppm (C2). Mass spectral analysis showed
gave [3,3,4- H ]-γ-octalactone in a disappointing 6% yield after
a molecular ion of m/z 143 (15%), 3 mass units above that of
purification by flash chromatography with 92% deuterium
1
1
1
-decene.
incorporation as judged by H NMR. Comparison of H NMR
spectra with that of unlabeled γ-octalactone showed the disap-
pearance of the one-proton multiplet at 4.46 ppm (H4) and the
two methylene multiplets at 1.88 and 2.31 ppm (H3). 13C NMR
showed splitting of the deuterated carbons with C4 appearing
as a 1:1:1 triplet at 80.5 ppm and C3 as a multiplet centered at
27.3 ppm. A molecular ion of m/z 145 (<1%) was obtained by
GC-MS, corresponding to the presence of three deuterium
atoms. Similarly, a base peak of m/z 88 (100%), increased by
3 mass units, was also observed (Figure 3B).
2
Using the optimized conditions described above, [1,1,2- H3]-
-decene (3.5 mmol) was refluxed with 2-iodoacetamide (1.2
1
mmol), ACCN (2.3 mmol), and water (0.1 mol) in benzene (23
2
mL) for 18 h under an atmosphere of nitrogen. [3,3,4- H3]-γ-
Dodecalactone was obtained in 23% yield after chromatography
and distillation with 96% deuterium incorporation as judged by
1
1
H NMR. The H NMR spectra showed the expected simplifica-
tion of splitting patterns with the disappearance of the one-proton
quintet at 4.31 ppm (H4) and two methylene multiplets at 1.82

7082 J. Agric. Food Chem., Vol. 52, No. 23, 2004
Hislop et al.
6
-(Z)-dodeceno-γ-lactone in 75% yield after reduction with
deuterium gas and Lindlar’s catalyst (16).
SIDA Evaluation. The use of the deuterated lactones in SIDA
2
of butter flavor was investigated. A sample of [2,2,3,3- H4]-γ-
2
decalactone and [3,3,4- H3]-γ-dodecalactone in heptane (10 µL)
were added to a stirred slurry of butter (28 g) at 40 °C so as to
-
1
give concentrations of internal standards of 36 and 90 ng g
of butter, respectively. A flavor extract was prepared by
adsorption of the butter onto Celite and extraction with
acetonitrile (22) and analyzed by GC-MS with selected ion
monitoring. The deuterated internal standards (m/z 88 and 89)
were fully resolved from their unlabeled analogues (m/z 85)
(Figure 4). Using appropriate response factors, the concentra-
tions of γ-decalactone and γ-dodecalactone in this sample were
-
1
calculated as 19 and 185 ng g , respectively.
This result demonstrates the suitability of both the [3,3,4-
H3]- and [2,2,3,3- H4]-γ-lactones for use in SIDAs, although
2
2
care must be taken to correct for any deuterium exchange that
2
may occur with the [2,2,3,3- H4]-labeled compounds. The [3,3,4-
2
H3]-γ-lactones are not subject to deuterium exchange, and a
2
good source of [1,1,2- H3]-1-alkenes and further optimization
of yields (23) would make these compounds more readily
available for use in flavor analysis.
ACKNOWLEDGMENT
We thank a reviewer for drawing our attention to further research
by Yorimitsu et al. (23), which reports the synthesis of
γ-decalactone in 83% yield by the free radical cyclization of
1-octene and 2-iodoacetamide using aqueous ethanol as solvent
and a novel radical initiator. We also thank John Allen for the
HRMS measurements
Figure 4. GC-MS-SIM mass chromatograms of a butter flavor extract
2
2
spiked with [2,2,3,3- H
4
]-
γ
-decalactone and [3,3,4- H
3
]-
γ
-dodecalactone
-
1
at 36 and 90 ng g butter, respectively. Unlabeled
and
decalactone at m/z 89 (D), and [3,3,4- H
B).
γ
-decalactone (C)
2
γ
-dodecalactone (A) were measured at m/z 85, [2,2,3,3- H
4
]-γ
-
2
3
]-γ-dodecalactone at m/z 88
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Received for review July 6, 2004. Revised manuscript received
September 7, 2004. Accepted September 8, 2004.
JF048885B