Synthesis of 13C and 15N multilabeled 5-aminolevulinic acid

Article abstract of DOI:10.1002/jlcr.541

5-[4-¹³C,¹⁵N]- and 5-[5- ¹³C,¹⁵N]Aminolevulinic acid (ALA) were simply synthesized in four steps by the condensation of [1-¹³C,¹⁵N]- or [2-¹³C,¹⁵N]glycine, respectively, with phthalic anhydride, followed by conversion to the chloride, coupling reaction with a three-carbon unit and hydrolysis. Copyright

Full text of DOI:10.1002/jlcr.541

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS
J Label Compd Radiopharm 2002; 45: 139–143.
DOI: 10.1002/jlcr.541
Research Article
13
15
Synthesis of C and N multilabeled
5-aminolevulinic acid
Katsumi Iida and Masahiro Kajiwara*
Department of Medicinal Chemistry, Meiji Pharmaceutical University,
2-522-1Noshio, Kiyose-shi, Tokyo 204-8588, Japan
Summary
5-[4-13C,15N]- and 5-[5-13C,15N]Aminolevulinicaidc (ALA) were simply
synthesized in four steps by the condensation of [1-13C,15N]- or [2-13C,15N]gly-
cine, respectively, with phthalic anhydride, followed by conversion to the
chloride, coupling reaction with a three-carbon unit and hydrolysis. Copyright
# 2002 John Wiley & Sons, Ltd.
Key Words: 5-[4-13C,15N]aminolevulinicaidc; 5-[5-
acid; [1-13C,15N]glycine; [2-13C,15N]glycine
13C,15N]aminolevulinic
Introduction
We have developed various methods for the synthesis of regioselectively
1,2
stable-isotope-labeled 5-aminolevulinicaidc (ALA),
which is a
precursor of porphyrins, for use in studies on the biosynthesis of
porphyrins.3–5 Syntheticmethods of ALA isotope-labeled on C-5 have
been reported by Shemin et al.,6 Battersby et al.7 and from our
laboratory,1 but involve many steps between introduction of the labeled
carbon and formation of the final product. We present here a simple
synthesis of [5-13C,15N]ALA from [2-13C,15N]glycine, and of
[4-13C,15N]ALA from [1-13C,15N]glycine.
*Correspondence to: M. Kajiwara, Department of Medicinal Chemistry, Meiji Pharmaceutical
University, 2-522-1 Noshio, Kiyose-shi, Tokyo 204-8588, Japan.
Copyright # 2002 John Wiley & Sons, Ltd.
Received 9 October 2001
Accepted 24 October 2001

140
K. IIDA AND M. KAJIWARA
Results and discussion
As shown in Scheme 1, the condensation of [2-13C,15N]glycine ð1Þ and
%
phthalicanhydride ð2Þ gave 2-[15N]phthalimido[2-13C]acetic acid ð3Þ in
%
%
86% yield. The transhalogenation of ethyl 3-bromopropionate ð5Þ with
%
sodium iodide in 2-butanone gave ethyl 3-iodopropionate ð6Þ in 95%
%
yield. The coupling reaction8,9 of 2-[15N]phthalimido[2-13C]acetyl
chloride ð4Þ, which was derived from 2-[15N]phthalimido[2-13C]acetic
%
acid ð3Þ and thionyl chloride, with 2-ethoxycarbonylethylzinc iodide,
which was derived from ethyl 3-iodopropionate ð6Þ treated with zinc–
copper couple, catalyzed by tetrakis(triphenylphosphine)palladium (0)
%
%
in dry toluene and dry N,N-dimethylacetamide gave ethyl 5-[15N]phtha-
limido[5-13C]levulinate ð7Þ in 92% yield. Finally, hydrolysis of ethyl
%
5-[15N]phthalimido[5-13C]levulinate ð7Þ in 6 N hydrochloric acid gave
%
[5-13C,15N]ALA ð8Þ in 89% yield. [4-13C,15N]ALA was similarly
%
synthesized from [1-13C,15N]glycine in four steps.
Experimental
Materials
[1-13C,15N]- and [2-13C,15N]Glycine (99 at% 13C, 99 at % 15N) were
purchased from Masstrace, Inc. All other chemicals were of analytical grade.
Instruments
Melting point determinations were carried on a Yanaco micro melting
point apparatus, Model MP; values are uncorrected. IR spectra were
Scheme 1. Synthesis of [5-13C,15N]ALA (8)
%
Copyright # 2002 John Wiley & Sons, Ltd.
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13C AND 15N-LABELED ALA
141
recorded on a Jasco VALOR-III FT-IR spectrometer. 1H-NMR
(300 MHz) and 13C-NMR (75 MHz) spectra were recorded on a Varian
GEMINI-300 spectrometer. EI- and FAB-MS spectra were obtained on
a Jeol DX302 spectrometer.
2-[15N]Phthalimido[2-13C]acetic acid (3)
%
[2-13C,15N]Glycine (1) (1.0 g, 13.0 mmol) and phthalicanhydride ( 2)
%
%
(2.0 g, 13.5 mmol) were heated at 1608C, until the whole was melted.
After cooling, the residue was recrystallized from water to give
2-[15N]phthalimido[2-13C]acetic acid (3) (2.3 g, 86%), m.p. 193–1958C;
%
1H-NMR (CDCl3) d : 4.49 (dd, 2H, J ¼ 142:3 Hz, J=1.1 Hz), 7.75–
7.92 (m, 4H); 13C-NMR (CDCl3) d :38.4 (d, J=13.3 Hz); FT-IR (KBr)
cmꢀ1: 1745, 2928; EI-MS m=z (rel. int. %): 207 (M+, 4), 162 (100).
Analytical data of 2-[15N]phthalimido[1-13C]acetic acid, m.p.
191–1948C; 1H-NMR (CDCl3) d : 4.50 (dd, 2H, 2J=5.8 Hz,
2J=1.1 Hz), 7.75–7.92 (m, 4H); 13C-NMR (CDCl3) d : 171.6; FT-IR
(KBr) cmꢀ1; 1726, 2926; EI-MS m=z (rel. int. %): 207 (M+, 4) 161
(100).
2
Ethyl 3-iodopropionate (6)
%
A suspension of ethyl 3-bromopropionate (5) (10 ml, 78.0 mmol) and
%
NaI (17 g, 113.4 mmol) in 2-butanone (100 ml) was refluxed at 908C for
16 h under argon. After cooling, the crystals were removed by filtration.
The filtrate was evaporated, diluted with ether, and washed with brine.
Distillation of the crude product gave ethyl 3-iodopropionate ð6Þ (33.7 g,
%
95%), b.p. 1058C (20 mm Hg); 1H-NMR (CDCl3) d :1.29 (t, 3H,
J=7.1 Hz), 2.97 (t, 2H, J=7.1 Hz), 3.34 (t, 2H, J=7.1 Hz), 4.19 (q, 2H,
J=7.1 Hz); FT-IR (neat) cmꢀ1: 1730; EI-MS m=z (rel. int. %): 228
(M+, 100), 155 (61), 101 (92), 73 (47).
Ethyl 5-[15N]phthalimido[5-13C]levulinate (7)
%
A mixture of 2-[15N]phthalimido[2-13C]acetic acid ð3Þ (2.3 g, 11.1 mmol)
%
and thionyl chloride (30 ml) was refluxed at 808C for 18 h. The excess
thionyl chloride was removed in vacuo. The residue was dissolved in dry
Copyright # 2002 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2002; 45: 139–143

142
K. IIDA AND M. KAJIWARA
toluene (3 ml) and evaporated. This process was repeated twice, and the
resulting 2-[15N]phthalimido[2-13C]acetyl chloride ð4Þ was dissolved in
%
dry toluene (5 ml) under argon. Ethyl 3-iodopropionate ð6Þ (2.82 g,
12.4 mmol) was added to a suspension of Zn–Cu couple (1.0 g) in dry
%
toluene (1.2 ml) and dry N; N-dimethylacetamide (14 ml) under argon,
and the mixture was heated at 608C for 15 h. To this suspension, a
suspension of Pd(PPh3)4 (530 mg, 459 mmol) in dry toluene (5 ml) under
argon was added, and the whole was stirred at 608C for 5 min. To this
suspension, a solution of 2-[15N]phthalimido[2-13C]acetyl chloride ð4Þ
%
was added, and the whole was stirred at 608C for 25 min. The reaction
was diluted with ethyl acetate (300 ml), and the whole was washed with
1 N HCl, sat. NaHCO3 and brine, dried over dry MgSO4, and
evaporated. Chromatography of the crude product on silica gel with
ethyl acetate:hexane (1 : 1) gave ethyl 5-[15N]phthalimido[5-13C]levuli-
1
nate ð7Þ (2.98 g, 92%), m.p. 75–778C; H-NMR (CDCl3) d : 1.26 (t, 3H,
%
J=7.1 Hz), 2.66 (t, 2H, J=6.6 Hz), 2.85 (t, 2H, J=6.6 Hz), 4.15 (q, 2H,
J=7.1 Hz), 4.56 (d, 2H, J=139.8 Hz), 7.73–7.89 (m, 4H); 13C-NMR
(CDCl3) d: 46.5 (d, J=12.2 Hz); FT-IR (KBr) cmꢀ1: 1725, 1771, 2920;
EI-MS m=z (rel. int. %): 291 (M+, 2), 162 (44), 129 (100), 101 (75).
Analytical data of ethyl 5-[15N]phthalimido[4-13C]levulinate, m.p.
1
73–768C; H-NMR (CDCl3) d: 1.26 (t, 3H, J=7.1 Hz) 2.67 (q, 2H,
J=6.6 Hz), 2.86 (q, 2H, J=6.6 Hz), 4.15 (q, 2H, J=7.1 Hz), 4.57 (dd,
2
2
2H, J=3.8 Hz, J=1.1 Hz), 7.73–7.89 (m, 4H); 13C-NMR (CDCl3) d:
200.8; FT-IR (KBr) cmꢀ1: 1726, 1770, 2916; EI-MS m=z (rel. int. %):
291 (M+, 1), 161 (100), 130 (50), 102 (37).
[5-13C,15N]ALA hydrochloride (8)
%
A solution of ethyl 5-[15N]phthalimido[5-13C]levulinate ð7Þ (1.38 g,
%
4.7 mmol) in 6 N HCl (6 ml) was refluxed at 1108C for 14 h. The
reaction mixture was cooled to room temperature and filtrated. The
filtrate was washed with ether and evaporated. The residue was
recrystallized from EtOH–ether to give [5-13C,15N]ALA hydrochloride
1
ð8Þ (717 mg, 89%), m.p. 144 –1478C; H-NMR (D2O) d: 2.72 (t, 2H,
%
J=6.2 Hz), 2.90 (t, 2H, J=6.2 Hz), 4.13 (d, 2H, J=143.9 Hz); 13C-
NMR (D2O) d: 49.8 (d, J=7.7 Hz); FT-IR (KBr) cmꢀ1: 1695, 1725,
2927; FAB-MS (glycerol) m=z: 134 (MH+-HCl).
Analytical data of [4-13C,15N]ALA hydrochloride, m.p. 146–1498C;
1H-NMR (D2O) d: 2.72 (q, 2H, J=6.0 Hz), 2.90 (q, 2H, J=6.0 Hz),
Copyright # 2002 John Wiley & Sons, Ltd.
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13C AND 15N-LABELED ALA
143
4.13 (d, 2H, J=4.2 Hz); 13C-NMR (D2O) d: 206.8; FT-IR (KBr) cmꢀ1
1685, 1725, 3005; FAB-MS (glycerol) m=z: 134 (MH+-HCl).
;
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Copyright # 2002 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2002; 45: 139–143