evaporated under reduced pressure to give hexanoic acid (371
mg, 77%) as a yellow oil; νmax/cmϪ1 3013br, 2958, 1713 and 1414;
m/z (EIϩ) 117 (Mϩ ϩ 1, 0.24%) and 60 (Mϩ Ϫ 56, 100);
δH (CDCl3) 0.89 (3 H, J 6.7, t, CH3), 1.32 [4 H, m, (CH2)2], 1.63
(2 H, m, CH2), 2.33 (2 H, t, J 6.2, CH2CO) and 11.0 (1 H, s,
CO2H); δC(CDCl3) 14.3 (C-6), 22.8 (C-5), 24.8 (C-4), 31.7 (C-3),
34.5 (C-2) and 181.2 (C-1). This material was derivatised with-
out further purification.
ment of [1-13C]octanoate with diazomethane, was added drop-
wise to a stirred solution of lithium diisopropylamide (11.8
mmol) in THF (50 ml) at Ϫ70 ЊC. After 5 min the reaction
mixture was allowed to warm to 18 ЊC at which temperature it
was stirred for 1 h. The reaction was quenched by the addition
of [1H]methanol (5 ml) to the mixture which was then stirred
for an additional 1 h. It was then poured into saturated aqueous
ammonium chloride (50 ml). The aqueous layer was extracted
with diethyl ether (2 × 50 ml) and the combined organic
extracts were dried (MgSO4), filtered and evaporated under
reduced pressure. The residue was purified by distillation (0.01
mmHg, 50 ЊC) to give methyl [1-13C,2-2H]octanoate (501 mg,
53%). This material was directly hydrolysed by treatment with
1 KOD in D2O (20 ml) under reflux for 12 h. After being
allowed to cool, the solution was washed with diethyl ether
(2 × 20 ml) and acidified with 50% aqueous HCl. The product
was then extracted into diethyl ether (3 × 20 ml) and the com-
bined ethereal extracts were then dried (MgSO4), filtered and
evaporated under reduced pressure to give [1-13C,2-2H1]-
octanoic acid (287 mg, 33%) as a clear oil; νmax/cmϪ1 3049br,
2956, 2928, 1668 and 1272; m/z (EIϩ) 146 (Mϩ, CHD, 0.99%)
and 145 (Mϩ, CH2, 0.51); δH (CDCl3) 0.88 (3 H, t, J 6.5,
CH3), 1.28 [8 H, m, (CH2)4], 1.61 (2 H, m, CH2) and 2.34 (1.1 H,
m, CHD); δC(CDCl3) 14.1 (C-8), 22.6 (C-7), 24.6 (C-6), 28.9
Methyl O-hexanoyl-(2R)-mandelate from deuterium labelled
hexanoic acid
Methyl (R)-mandelate (221 mg, 1.33 mmol) and dicyclohexyl-
carbodiimide (275 mg, 1.33 mmol) were added to a stirred solu-
tion of the hexanoic acid (115 mg, 1.33 mmol) and 4-dimethyl-
aminopyridine (5 mg, 0.04 mmol) in dichloromethane (7 ml) at
Ϫ10 ЊC. The reaction mixture was stirred at this temperature
for 3 h after which precipitated urea was filtered off. The filtrate
was re-evaporated under reduced pressure and the residue sus-
pended in dichloromethane (3 ml) and the solution refiltered.
After evaporation of the filtrate the residue was purified over
silica gel eluting with dichloromethane; evaporation of the
active fractions afforded methyl O-hexanoyl-(2R)-mandelate
(227 mg, 65%) as a colourless oil; νmax/cmϪ1 2955, 2932, 1745,
1455, 1216 and 1160; m/z (CI) 285 [(M ϩ 3)ϩ ϩ 18, 3.1%], 284
[(M ϩ 2)ϩ ϩ 18, 3.71], 283 [(M ϩ 1)ϩ ϩ 18, 13.9], 282 (Mϩ ϩ
18, 40.9) and 166 (Mϩ Ϫ 99, 100); δH (CDCl3) 0.9 (3 H, t, J 6,
CH3), 1.33 [4 H, m, (CH2)2], 1.70 (2 H, m, CH2), 2.47 (2 H, dq, J
7.46 and 3.94, CH2), 3.72 (3 H, s, OMe), 5.95 (1 H, s, CH) and
7.40 (5 H, m, Ar); δD (CCl4) (see Fig. 3), 0.92 (CD3), 1.39 (CHD)
and 2.46 (CHD); δC(CDCl3) 14.4 (C-12), 22.8 (C-11), 25.0
(C-10), 31.7 (C-9), 34.4 (C-8), 53.1 (OMe), 74.7 (C-2), 128.1
(C-4), 129.3 (C-5), 129.6 (C-6), 134.4 (C-3), 169.8 (C-7 or C-1)
and 173.7 (C-7 or C-1) [Found (from unlabelled analysis): Mϩ,
265.1426. C15H21O4 requires M Hϩ 265.1439].
13C,13
C
13C,2H
(C-5), 29.0 (C-4), 31.6 (C-3), 33.8 (dt, J
54.6, J
13C,13
19.3, CHD, C-2), 34.0 (d, J
C 54.6, C-2) and 180.3 (enriched
C-1).
Acknowledgements
We thank Dr Raymond L. Edwards of the University of Brad-
ford for a gift of the P. piliformis and X. mali cultures and Drs
John Parkinson and Ian Sadler of The University of Edinburgh
for recording 13C-{1H,2H} NMR spectra. We also thank Dr
Kevin A. Reynolds, University of Maryland at Baltimore, for
fruitful discussions and the EPSRC for funding a studentship
(N. C. J. E. C.).
DL-[3-13C,2H3]Alanine
A solution of LDA (6.8 mmol), generated from diisopro-
pylamine (0.69 g, 0.95 ml, 6.8 mmol) and butyllithium (1.6 in
hexanes; 4.2 ml, 6.8 mmol) in THF (10 ml), was transferred to a
stirred solution of 1-benzyl-2-(tert-butyl)-3-methylimidazolin-
4-one (1.61 g, 6.16 mmol) in THF (70 ml) at Ϫ78 ЊC. The
reaction mixture was stirred for 1 h after which [13C,2H3-
methyl]iodomethane (1.0 g, 6.85 mmol) was added dropwise.
The solution was stirred at Ϫ78 ЊC for 45 min and was then
allowed to warm gradually to 18 ЊC; it was then left at ambient
temperature for 12 h after which the reaction was quenched by
the addition of saturated aqueous NH4Cl (70 ml) to the mix-
ture. The aqueous layer was extracted into diethyl ether (2 × 80
ml) and the combined organic extracts were dried (MgSO4),
filtered and evaporated under reduced pressure. Purification of
the residue over silica gel with diethyl ether–light petroleum–
methanol (60:35:5) gave 1-benzyl-2-(tert-butyl)-3,5-dimethyl-
[5-13C,2H3]imidazolidin-4-one as an amorphous white solid
(0.98 g, 56%); mp 145.5–146.5 ЊC (lit.,18 145.6–146.2 ЊC); m/z
(CI) 279 (Mϩ ϩ 1, 100%) [Found (unlabelled material): C,
69.90; H, 8.15; N, 10.01. C15H20O2N2 requires C, 70.04; H, 8.08;
N, 10.21%].
References
1 R. Anderson, R. L. Edwards and A. J. S. Whalley, J. Chem. Soc.,
Perkin Trans 1, 1985, 1481.
2 M. Rohr, Dissertation, Eidgenössische Techische Hochschule Prom.
N., Zurich, 1973, 5112.
3 D. Arigoni, Pure Appl. Chem., 1975, 41, 219.
4 M. Tanabe, T. Hamasaki and Y. Suzuki, J. Chem. Soc., Chem.
Commun., 1973, 212.
5 Y. Asahina and S. Shibata, Chemistry of the Lichen Substances,
Japanese Society for the Promotion of Science, Ueno, Tokyo, 1954.
6 J. L. Bloomer, W. R. Eder and W. F. Hoffman, J. Chem. Soc. C,
1970, 1848; J. L. Bloomer, W. R. Eder and W. F. Hoffman, J. Chem.
Soc., Chem. Commun., 1968, 354; J. L. Bloomer and W. F. Hoffman,
Tetrahedron Lett., 1969, 50, 4339.
7 H. Thomas, J. Pharm. Soc., Jpn, 1940, 60, 318.
8 S. B. Singh, Tetrahedron Lett., 1993, 34, 6524; S. B. Singh,
D. L. Zink, J. M. Liesch, M. A. Goetz, R. G. Jenkins, M. Nallin-
Omstead, K. C. Silverman, G. F. Bills, R. T. Mosely, J. B. Gibbs,
G. Albers-Schonberg and R. B. Lingham, Tetrahedron, 1993, 49,
5917.
1-Benzyl-2-(tert-butyl)-3,5-dimethyl[5-13C,2H3]imidazolidin-
4-one (0.97 g, 3.5 mmol) was heated with 6 aqueous HCl (6
ml) to 180 ЊC in a sealed tube for 12 h. The solution was then
removed and concentrated under reduced pressure. Purification
of the residue by ion exchange chromatography (Dowex 50X2-
400) gave -[3-13C,2H3]alanine (245 mg, 70%) as an amor-
phous white solid, mp 289–290 ЊC (decomp.) [lit.,23 295–
296 ЊC (decomp.)]; m/z (CI) 94 (Mϩ ϩ 1, 100%); δH (D2O) 3.62
9 J. C. Vederas, Nat. Prod. Rep., 1987, 4, 277; M. J. Garson and
J. Staunton, Chem. Soc. Rev., 1979, 539.
10 K. Arai, B. J. Rawlings, Y. Yoshizawa and J. C. Vederas, J. Am.
Chem. Soc., 1989, 111, 3391.
11 B. J. Rawlings, P. B. Reese, S. E. Ramer and J. C. Vederas, J. Am.
Chem. Soc., 1989, 111, 3382; P. B. Reese, B. J. Rawlings, S. E. Ramer
and J. C. Vederas, J. Am. Chem. Soc., 1988, 110, 316.
12 M. Gonzalez-de-la-Parra and C. R. Hutchinson, J. Am. Chem. Soc.,
1986, 108, 2448; C. R. Hutchinson, L. Shu-Wen, A. G. McInnes and
J. A. Walter, Tetrahedron, 1983, 39, 3507.
2
1
H,13C
13C,2H
(1 H, br d,
J
4, CH); δC(D2O) 18.2 (septet, J
19.6,
13 C. A. Townsend, S. W. Brobst, S. E. Ramer and J. C. Vederas, J. Am.
Chem. Soc., 1988, 110, 318.
13C,13
C-3), 53.13 (d, J C 34.7, C-2) and 178.63 (C-1).
14 S. W. Brobst and C. A. Townsend, Can. J. Chem., 1994, 72, 200.
15 C. M. H. Watanabe, D. Wilson, J. E. Linz and C. A Townsend,
Chem. Biol., 1996, 3, 463; J. Yu, P.-k. Chang, J. W. Cary,
[1-13C,2-2H]Octanoic acid
Methyl [1-13C]octanoate (0.94 g, 5.9 mmol), prepared by treat-
J. Chem. Soc., Perkin Trans. 1, 1997
833