The First Synthesis of Optically Active 1-Substituted Taurines 469
the determination of 2-(benzyloxycarbonyl)amino-
1-methylethyl thioacetates with (R)-3b (t = 33.79
min), and (S)-3b (t = 36.89), flow rate: 0.6 mL/min.
(S)-2-(Benzyloxycarbonyl)amino-1-methylethyl
Thioacetate (S)-3b. Colorless oil, yield 67%, >99%
ee. Rf = 0.25 (petroleum ether: ether = 4:1, silica
gel plate). [α]2D5 = −29.5 (c, 1.13, CHCl3). IR (KBr): ν
3342 (NH), 1720 (C O), 1693 (C O) cm−1; 1H NMR
(300 MHz, CDCl3) δ 7.40–7.27 (m, 5H, Ph), 5.10 (s,
2H, OCH2), 5.02 (s, br, 1H, NH), 3.66 (ddq, J = 6.3,
6.9, 6.9 Hz, 1H, CH), 3.43 (ddd, J = 5.7, 6.3, 13.9
Hz, 1H in NCH2), 3.31 (ddd, J = 6.9, 6.9, 13.9 Hz,
1H in NCH2), 2.30 (s, 3H, COCH3), 1.30 (d, J = 6.9
Hz, 3H, CH3); 13C NMR (75.5 MHz, CDCl3) δ 195.69,
156.41, 136.35, 128.45, 128.07, 127.98, 66.73, 46.08,
39.72, 30.68, 18.06; MS (EI) m/z: 267 (M+, 1.1), 224
(M+-Ac, 1.2), 191 (M+-AcSH, 9.3), 108 (PhCH2OH+,
13.7), 107 (PhCH2O+, 8.2), 91 (PhCH2+, 100). Anal.
Calcd for C13H17NO3S (267.35): C, 58.40; H, 6.41; N,
5.24. Found: C, 58.51; H, 6.70; N, 5.09%.
(R)-2-(Benzyloxycarbonyl)amino-1-phenylethyl
Thioacetate (R)-3a. Colorless crystal; yield 67%,
mp 73–74◦C, >99% ee. Rf = 0.30 (petroleum ether:
ether = 3:1, silica gel plate). [α]2D5 = −126 (c, 1.12,
CHCl3). IR (KBr): ν 3343 (NH), 1720 (C O), 1695
(C O) cm−1; 1H NMR (300 MHz, CDCl3) δ 7.32–7.29
(m, 10H, ArH), 5.08 (s, 2H, OCH2), 4.96 (s, 1H,
NH), 4.72 (t, J = 7.5 Hz, 1H, CH), 3.68 (dd, J = 6.9,
7.5 Hz, 2H, NCH2), 2.30 (s, 3H, CH3); 13C NMR
(75.5 MHz, CDCl3) δ 194.33, 156.09, 138.46, 136.38,
128.77, 128.64, 128.38, 127.98, 127.84, 127.79, 66.69,
47.81, 45.55, 30.34; MS (EI) m/z: 329 (M+, 1.2), 286
(M+-Ac, 14.9), 253 (M+-AcSH, 1.1), 238 (M+-PhCH2,
19.8), 108 (PhCH2OH+, 5.9), 91 (PhCH+2 , 100). Anal.
Calcd for C18H19NO3S (329.41): C, 65.63; H, 5.81; N,
4.25. Found: C, 65.51; H, 5.71; N, 4.46%.
General Procedure for Synthesis of Optically
Active 1-Substituted Taurines (R)- and (S)-4
(S)-2-(Benzyloxycarbonyl)amino-1-phenylethyl
Thioacetate (S)-3a. Colorless crystal; yield 63%,
mp 72.5–73.5◦C, >99% ee. Rf = 0.30 (petroleum
ether: ether = 3:1, silica gel plate). [α]2D5 = +122 (c,
0.72, CHCl3). IR (KBr): ν 3342 (NH), 1718 (C O),
1696 (C O) cm−1; 1H NMR (300 MHz, CDCl3) ꢀ
7.32–7.29 (m, 10H, ArH), 5.08 (s, 2H, OCH2), 4.96
(s, 1H, NH), 4.72 (t, J = 7.5 Hz, 1H, CH), 3.68 (dd,
J = 6.9, 7.5 Hz, 2H, NCH2), 2.30 (s, 3H, CH3);13C
NMR (75.5 MHz, CDCl3) δ 194.27, 156.09, 138.46,
136.38, 128.77, 128.64, 128.38, 127.98, 127.84,
127.79, 66.69, 47.81, 45.55, 30.34; MS (EI) m/z: 329
(M+, 1.2), 286 (M+-Ac, 14.8), 253 (M+-AcSH, 1.2),
238 (M+-PhCH2, 19.8), 108 (PhCH2OH+, 5.9), 91
(PhCH+2 , 100). Anal. Calcd for C18H19NO3S (329.41):
C, 65.63; H, 5.81; N, 4.25. Found: C, 65.51; H, 5.69;
N, 4.05%.
To a performic acid solution, prepared by mixing
and stirring 30% H2O2 (1.2 mL) and 88% HCO2H
(12 mL) at room temperature for 1 h and cooled in
an ice bath were added thioacetate derivatives 3 (2
mmol) in 88% HCO2H (2.7 mL) dropwise, the result-
ing mixture was refluxed and stirred overnight. After
removal of solvent and washing with chloroform, the
residue was crystallized from methanol to give the
pure 1-substituted taurines 4.
(R)-2-Amino-1-phenylethanesulfonic Acid (R)-4a.
Colorless crystal; yield: 96%; mp >360◦C. [α]D25
=
−4.98 (c, 0.91, H2O). IR (KBr): ν 3424, 3217, 3061
+
1
(NH3 ), 1212 (SO2), 1170 (SO2) cm−1; H NMR (300
MHz, DMSO-d6) δ 7.78 (s, br, 3H, NH3), 7.29 (s, 5H,
ArH), 3.88 (dd, J = 4.5, 9.9 Hz, 1H, H in CH2), 3.45
(d, J = 4.5 Hz, 1H, H in CH2), 3.08 (d, J = 9.9 Hz,
1H, CH); 13C NMR (75.5 MHz, DMSO-d6) δ 136.11,
129.06, 127.93, 127.21, 61.56, 40.88. MS (ESI, posi-
tive ion) m/z: 202 (MH)+. Anal. Calcd for C8H11NO3S
(201.24): C, 47.75; H, 5.51; N, 6.96. Found: C, 47.60;
H, 5.77; N, 7.14%.
(R)-2-(Benzyloxycarbonyl)amino-1-methylethyl
Thioacetate (R)-3b. Colorless oil, yield 54%, >99%
ee. Rf = 0.25 (petroleum ether: ether = 4:1, silica
gel plate). [α]2D5 = +29.7 (c, 1.22, CHCl3). IR (KBr): ν
3344 (NH), 1721 (C O), 1692 (C O) cm−1; 1H NMR
(300 MHz, CDCl3) δ 7.40–7.27 (m, 5H, Ph), 5.10 (s,
2H, OCH2), 5.02 (s, br, 1H, NH), 3.66 (ddq, J = 6.3,
6.9, 6.9 Hz, 1H, CH), 3.43 (ddd, J = 5.7, 6.3, 13.9
Hz, 1H, H in NCH2), 3.31 (ddd, J = 6.9, 6.9, 13.9
Hz, 1H, H in NCH2), 2.30 (s, 3H, COCH3), 1.30 (d,
J = 6.9 Hz, 3H, CH3); 13C NMR (75.5 MHz, CDCl3)
δ 195.69, 156.41, 136.35, 128.45, 128.07, 127.98,
66.73, 46.08, 39.72, 30.68, 18.06; MS (EI) m/z: 267
(M+, 1.2), 224 (M+-Ac, 1.2), 191 (M+-AcSH, 9.2), 108
(PhCH2OH+, 13.7), 107 (PhCH2O+, 8.2), 91 (PhCH+2 ,
100). Anal. Calcd for C13H17NO3S (267.35): C, 58.40;
H, 6.41; N, 5.24. Found: C, 58.61; H, 6.29; N, 5.09%.
(S)-2-Amino-1-phenylethanesulfonic Acid (S)- 4a.
Colorless crystal; yield: 92%; mp >360◦C. [α]D25
=
+4.80 (c, 0.77, H2O). IR (KBr): ν 3421, 3215, 3058
+
1
(NH3 ), 1214 (SO2), 1170 (SO2) cm−1; H NMR (300
MHz, DMSO-d6) δ 7.82 (s, br, 3H, NH3), 7.29 (s, 5H,
ArH), 3.88 (dd, J = 4.5, 9.9 Hz, 1H, H in CH2), 3.46
(m, 1H, H in CH2), 3.09 (d, J = 9.9 Hz, 1H, CH); 13
C
NMR (75.5 MHz, DMSO-d6) δ 136.09, 129.07, 127.95,
127.30, 61.59, 40.91. MS (ESI, positive ion) m/z: 202
(MH)+. Anal. Calcd for C8H11NO3S (201.24): C, 47.75;
H, 5.51; N, 6.96. Found: C, 47.50; H, 5.79; N, 7.04%.