CONTROLLED SYNTHESIS
941
with 0.5 M ammonia solution.23 The eluates containing the amino acids were
collected to afford 2b (45.2 mg, 80%) that showed a major peak in HPLC
(tr ¼ 8:8 min; 95%) accompanied by a minor peak (tr=22.3 min; 5%)
corresponding to the dichloroderivative 3b. Purification of a sample by
preparative HPLC gave pure 2b : [a]D22=ꢀ23.57 (c 1, H2O); ESI/MS
(negative) m/z (relative intensity): 441.0 (60, [35Cl]M+[37Cl]M-H+), 439.0
(100, [35Cl]M+[35Cl]M-H+), 222.0 (27, [37Cl]M-H+), 220.3 (85, [35Cl]M-H+);
1H-NMR (D2O): d 7.23–6.49 (3H, m, 20-H, 50-H and 60-H), 4.26 (1H, dd,
J ¼ 7:7 and 5.6, 2-H), 3.21 (1H, dd, J ¼ 14:9 and 5.6, 3-Ha), 3.08 (1H, dd,
J ¼ 14:9 and 7.7, 3-Hb); 13C-NMR (D2O): d 171.9 (s, 1-C), 152.4 (dd, J ¼ 68:7
and 64.8, 40-C), 131.4 (dd, J ¼ 64:8 and 57.2, 20-C), 129.9 (ddd, J ¼ 57:2, 57.2
and 7.6, 60-C), 128.2 (ddd, J ¼ 57:2, 57.2 and 7.6, 10-C), 121.4 (ddd, J ¼ 74:4,
67.7 and 6.7, 30-C), 118.1 (ddd, J ¼ 63:9, 58.2 and 5.7, 50-C), 56.7 (s, 2-H), 36.0
(d, J ¼ 43:9, 3-H).
Preparation of the 3-chloro-l-tyrosine-ring-[ring-13C6] (2b), via the chlorina-
tion of benzyl 4-(4-hydroxybenzyl-[ring-13C6])-5-oxo-1,3-oxazolidine-3-car-
boxylate (7)
(a) Benzyloxycarbonylation
of
the
(2S)-2-amino-3-(4-hydroxyphenyl-
[ring-13C6])-propionic acid methyl ester (4) hydrochloride. The methyl ester
hydrochloride 4 (60 mg; 0.25 mmol) was dissolved in an aqueous solution of
NaHCO3 (2 ml, 0.3 M) and the solution cooled to 08C. Then, benzyl
chloroformate (45 ml, 0.32 mmol) was added under stirring and the solution
kept at room temperature for 5 h. After extraction with ethyl acetate, the
organic layers were then washed with water and dried over Na2SO4.
Evaporation of the solvent under reduced pressure afforded a crude oil which,
after column chromatography (eluting with hexane/ethyl acetate, 60/40, v/v),
gave the pure methyl (2S)-2-benzyloxycarbonylamino-3-(4-hydroxyphenyl-
[ring-13C6])propanoate 6 (40.1 mg, 48.0%): mp 90.5–91.58C, [(lit.24 mp 91–
928C)]; [a]D22=+37.8 (c 1, CHCl3); ESI/MS (negative) m/z (relative
1
intensity): 669.1 (100, M+M-H+), 334.3 (72, M-H+); H-NMR (CDCl3): d
7.36–7.29 (5H, m, aromatics), 6.92 (2H, dd, J ¼ 155:6 and 7.5, 20-H and 60-H),
6.69 (2H, dd, J ¼ 161:7 and 6.0, 30-H and 50-H), 5.37 (1H, d, J ¼ 8:2, NH),
5.11 (1H, d, J ¼ 12:3, A part of a AB system, NHCO2CHHC6H5), 5.07 (1H, d,
J ¼ 12:3, B part of a AB system, NHCO2CHHC6H5), 4.63 (1H, ddd, J ¼ 8:2,
6.1 and 5.4, 2-H), 3.71 (3H, s, OCH3), 3.06 (1H, dd, J ¼ 13:9 and 5.4, 3-Ha),
2.98 (1H, dd, J ¼ 13:9 and 6.1, 3-Hb); 13C-NMR (CDCl3): d 172.43 (s,
COOCH3), 156.0 (dt, J= 64.8 and 9.5, 40-C), 131.1 (ddd, J ¼ 57:2, 57.2 and
5.7, 20-C and 60-C), 127.7 (dt, J ¼ 57:2 and 9.5, 10-C), 116.2 (ddd, J ¼ 64:8,
64.8 and 5.7, 30-C and 50-C), 67.1 (s, OCH2Ph), 54.9 (s, OCH3), 52.4 (s, 2-C),
37.5 (s, 3-C). Analytically calculated for 12C12 13C6H19NO5: C 65.64, H 5.81, N
4.25. Found: C 65.42, H 5.72, N 4.54.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 935–945