Synthesis of 4-thialysine from glycine
311
30 min. The reaction mixture was warmed to room tem-
perature and stirred for a further 12 h. The solvent was
evaporated under reduced pressure to produce the product
1 as white needle-like crystals (yield = 3.65 g, 99%).
Found: C, 32.08; H, 6.89; N, 9.99. Anal. Calcd. for
C133CH10ClNO2: C, 34.88; H, 7.17; N, 9.96. IR (KBr,
cm-1): 2,800–3,100 (br), 1,745, 1,576, 1,549, 1,501, 1,457,
1,423, 1,404, 1,384, 1,250, 1,040, 900, 854. 1H NMR
IR (KBr, cm-1): 3,352, 2,978, 2,933, 2,877, 1,690, 1,525,
1,456, 1,393, 1,367, 1,277, 1,252, 1,172, 1,140 (sh) 1,063,
864, 781, 756, 720–580 (br). 1H NMR (400 MHz, CDCl3):
1
d 1.45 (s, 9H), 2.40 (bs, 1H), 3.28 (dt, 2H, JCH
=
3
3
137.1 Hz, JHH = 4.6 Hz), 3.70 (t, 2H, JHH = 5.3 Hz),
5.01 (bs, 1H). 13C NMR (100 MHz, CDCl3) d 28.38, 43.21,
62.65 (d, JCC = 42.0 Hz), 79.74, 156.89.
1
2
(400 MHz, D2O): d 1.14 (t, 3H, JHH = 7.2 Hz), 3.75 (d,
2-Amino[2-13C]ethanol hydrochloride (4)
1
2
2H, JCH = 145.8 Hz), 4.14 (q, 2H, JHH = 7.2 Hz). 13C
NMR (100 MHz, D2O) d 13.13, 40.13, 63.24, 168.12 (d,
1JCC = 62.0 Hz). MALDI-TOF MS: m/z = 104.779
(calcd. for [M–Cl]? 105.075).
HCl gas was bubbled through a solution of 3 (1.38 g,
8.5 mmol) in CH2Cl2 for 30 min. The completion of
reaction was indicated by the formation of large amount of
solid formation. The solid was filtered under vacuum and
washed with CH2Cl2 (10 mL) to produce the product 4 as
white solid. (yield = 0.82 g, 98%). Found: C, 22.38; H,
8.42; N, 12.90. Anal. Calcd for C13CH8ClNO: C, 25.39; H,
8.18; N, 14.21. IR (KBr, cm-1): 3,848, 3,741, 3,412, 3,070,
1,624, 1,502, 1,316, 1,262, 1,105, 1,056, 999, 863, 814,
Ethyl 2-(tert-butoxycarbonylamino)[2-13C]acetate (2)
Triethylamine (4.5 mL, 32.3 mmol) was added slowly to a
solution of 1 (1.80 g, 12.8 mmol) in methanol (11 mL) at
4°C. To this mixture di-tert-butyl dicarbonate (3.0 mL,
13.1 mmol) was added slowly. The resultant mixture was
stirred under nitrogen for 24 h. The solvent was evaporated
in vacuo. Water (10 mL) and EtOAc (10 mL) were added
to the above residue, acidified with 1 N HCl solution (pH
5–6). The organic layer was separated and the aqueous
layer was extracted with EtOAc (10 mL). The combined
EtOAc extract was washed with 1 N HCl, 5% NaHCO3 and
brine, respectively. The organic layer was then dried over
anhydrous MgSO4 and concentrated to afford the product 2
as colorless oil. (yield = 2.52 g, 96%). Found: C, 52.23; H,
8.56; N, 7.41. Anal. Calcd. for C183CH17NO4: C, 53.42; H,
8.39; N, 6.86. IR (KBr, cm-1): 3,375, 2,980, 2,935, 1,753,
1,720, 1,702 (sh), 1,519, 1,455, 1,392, 1,368, 1,350, 1,283,
1,251, 1,203, 1,169, 1,052, 1,029, 945, 863, 784, 764,
1
765, 708, 652, 615, 593, 554, 499. H NMR (400 MHz,
1
3
D2O): d 2.99 (dt, 2H, JCH = 144.1 Hz, JHH = 5.4 Hz),
3
3.67 (t, 2H, JHH = 5.2 Hz). 13C NMR (100 MHz, D2O)
1
d 41.20, 57.51 (d, JCC = 38.0 Hz). MALDI-TOF MS:
m/z = 62.747 (calcd. for [M–Cl]? 63.064).
2-Bromo[1-13C]ethylamine hydrobromide (5)
Forty-eight percent hydrobromic acid (6.6 mL) was added
to 4 (788 mg, 8.0 mmol) in a 10-mL round bottom flask
attached to a distillation assembly and heated in an oil bath
until 1.5 mL distillate was collected. Then the temperature
was lowered and maintained in such a way so that it ceased
to distill and merely refluxed. After refluxing for 1 h,
1.4 mL more was distilled and the solution was heated
under reflux for 1 h. This procedure was repeated for 1,
0.7, 0.3 and 0.2 mL, respectively. During all these opera-
tions, precaution should be taken so that the temperature of
the oil bath does not exceed 160°C as the compound
decomposes. The last three portions of distillate were dis-
tilled under reduced pressure. The reaction mixture was
cooled to 70°C and acetone was added and stirred well.
After standing overnight at 4°C, it was filtered to obtain the
product as white solid which was washed with acetone and
air dried. Concentrating the filtrate to syrup, adding acetone
and standing overnight at 4°C, a second crop of material
was obtained. Compound 5 is hygroscopic. (yield =
1.01 g, 61%). Found: C, 11.58; H, 3.40; N, 6.75. Anal.
Calcd. for C13CH7Br2N: C, 12.15; H, 3.43; N, 6.80. IR
(KBr, cm-1): 3,427, 3,100–2,750 (br), 1,930–1,830 (br),
1,580, 1,560, 1,504, 1,483, 1,432, 1,373, 1,320, 1,251,
1,231, 1,088, 1,032, 935, 869, 819, 763, 708, 651, 570, 496.
1H NMR (400 MHz, D2O): d 3.15 (t, 1H, 3JHH = 6.1 Hz),
3.50–3.57 (m, 3H). 13C NMR (100 MHz, D2O) d 27.84
1
530–620 (br). H NMR (400 MHz, CDCl3): d 1.26 (t, 3H,
1
3JHH = 7.1 Hz), 1.43 (s, 9H), 3.88 (dt, 2H, JCH
=
3
3
145.7 Hz, JHH = 5.5 Hz), 4.19 (q, 2H, JHH = 7.2 Hz),
5.01(br, 1H). 13C NMR (100 MHz, CDCl3) d 14.16, 28.31,
42.29, 43.86, 61.34, 79.97, 155.72.
2-(tert-Butoxycarbonylamino)[2-13C]ethanol (3)
To a solution of 2 (2.50 g, 12.3 mmol) in THF (13 mL)
were added sodium borohydride (1.39 g, 36.6 mmol),
lithium chloride (1.55 g, 36.6 mmol) and methanol
(25 mL). The mixture was stirred at room temperature for
28 h. 15 mL of 5% citric acid was added to the reaction
mixture and extracted with CH2Cl2. The organic extract
was washed with 5% NaHCO3 and brine, respectively,
dried over anhydrous MgSO4 and concentrated to afford
the crude product as colorless oil. The crude product was
used for the next step without further purification.
(yield = 1.46 g, 73%). Found: C, 49.08; H, 9.49; N, 9.03.
Anal. Calcd. for C163CH15NO3: C, 52.45; H, 9.32; N, 8.64.
123