466
M. Oba et al. / Tetrahedron: Asymmetry 24 (2013) 464–467
Table 1
with 3% aqueous HCl and evaporated in vacuo to give crude amino
Crystal and diffraction parameters of 6
acid 2. Di-tert-butyl dicarbonate (Boc2O, 8.27 g, 37.9 mmol) and
K2CO3 (5.24 g, 38.0 mmol) were added to a stirred solution of the
crude amino acid in H2O (8 mL) and acetone (12 mL). After being
stirred at room temperature for 3 d, the acetone was evaporated
and the solution was washed with n-hexane. The solution was
acidified with citric acid, extracted with CHCl3, and dried over
MgSO4. Removal of the solvent afforded crude ( )-5 (1.57 g, 97%),
which was used for the next reaction without further purification.
Colorless crystals; IR (KBr) 3314, 2978, 2932, 1713, 1659 cmꢀ1; 1H
NMR (400 MHz, CDCl3) d 5.09 (br s, 1H), 3.39 (d, J = 11.7 Hz, 1H),
3.02 (d, J = 11.7 Hz, 1H), 2.98 (br s, 2H), 2.62 (br s, 1H), 2.39 (m,
1H), 1.45 (s, 9H); FAB(+)HRMS Calcd for C10H18NO4S (M++H)
248.0957, found 248.0934.
Empirical formula
Formula weight
Crystal dimensions (mm)
Crystal system
a, b, c (Å)
C23H33NO4S
419.56
0.16 ꢂ 0.11 ꢂ 0.07
Orthorhombic
10.17, 11.79, 19.00
2277.8
P212121
4
1.223
0.170
V (Å3)
Space group
Z value
Dcalcd (g/cm3)
l
(MoK
a
) (cmꢀ1
)
No. of observation
No. of variables
R1, Rw
4561 (I>2r(I))
262
0.0406, 0.0859
n-Hexane/EtOAc
Solvent
4.2.4. 3-(Benzyloxycarbonylamino)tetrahydrothiophene-3-carb-
oxylic acid (R)-20-hydroxy-[1,10]-binaphthyl ester 5
1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide
hydrochlo-
ride (EDC, 2.29 g, 12.0 mmol), DMAP (1.32 g, 10.8 mmol), and
(R)-BINOL (3.34 g, 11.6 mmol) were added to a stirred solution of
( )-3 (2.51 g, 8.93 mmol) in THF (60 mL), and the solution was stir-
red at room temperature for 2 d. The solution was then evaporated,
diluted with CHCl3, washed with 2% aqueous HCl, 5% aqueous NaH-
CO3, and brine, and dried over MgSO4. Removal of the solvent
afforded a residue, which was purified by column chromatography
on silica gel (400 g, 14% EtOAc in hexane) to give less polar-5
(1.96 g, 30%) and more polar-5 (1.96 g, 30%) as colorless crystals.
Less polar-5: mp 86–88 °C; TLC (SiO2, 25% EtOAc in hexane):
Rf = 0.364; ½a 2D6
ꢁ
¼ þ4:61 (c 1.06, MeOH); IR (KBr) 3387, 3059,
3034, 2947, 1759, 1717, 1508 cmꢀ1
;
1H NMR (500 MHz, CDCl3) d
8.05 (m, 1H), 7.98 (d, J = 8.0 Hz, 1H), 7.88 (d, J = 8.9 Hz, 1H), 7.83
(d, J = 8.0 Hz, 1H), 7.53 (m, 1H), 7.39–7.29 (m, 10H), 7.23 (d,
J = 8.2 Hz, 1H), 7.04 (d, J = 8.5 Hz, 1H), 5.12 (d, J = 9.6 Hz, 2H),
5.05 (br s, 1H), 5.04 (br s, 1H), 2.63–2.60 (m, 2H), 2.54–2.48 (m,
2H), 1.94 (m, 1H), 1.64 (m, 1H); 13C NMR (100 MHz, CDCl3) d
170.2, 155.2, 151.7, 147.8, 135.9, 133.3, 133.2, 132.3, 130.8,
130.3, 128.8, 128.6, 128.5, 128.3, 128.2, 128.1, 128.0, 127.9,
127.4, 126.8, 126.3, 125.6, 124.5, 123.6, 122.6, 121.6, 118.1,
113.6, 68.1, 67.1, 38.4, 38.1, 28.4; FAB(+)HRMS Calcd for
Figure 2. X-ray diffraction structure of 6.
none (22.8 g, 220 mmol) in ethanol (60 mL)/H2O (80 mL) and stir-
red at 50 °C for 5 d. The resultant precipitate was isolated by filtra-
tion. A second crop was obtained from the filtrate by filtration of
the resultant precipitate. The combined resultant (63.2 g, 82%)
was used for the next reaction without further purification: Color-
less crystals; mp 248–250 °C; IR (KBr) 3245, 3193, 3075, 2944,
C
33H28NO5S (M++H) 550.1688, found 550.1703. More polar-5: mp
80–82 °C; TLC (SiO2, 25% EtOAc in hexane): Rf = 0.303;
¼ þ12:9 (c 1.05, MeOH); IR (KBr) 3394, 3059, 3034, 2947,
1759, 1717, 1508 cmꢀ1 1H NMR (500 MHz, CDCl3) d 8.05 (m,
1
2770, 1778, 1732 cmꢀ1; H NMR (400 MHz, DMSO-d6) d 10.85 (br
½ ꢁ
a 2D6
s, 1H), 8.46 (s, 1H), 3.07 (d, J = 11.2 Hz, 1H), 3.02–2.92 (m, 2H),
2.84 (d, J = 11.2 Hz, 1H), 2.16–2.02 (m, 2H); DART(+)HRMS Calcd
for C6H9N2O2S (M++H) 173.0385, found 173.0372.
;
1H), 7.98 (d, J = 8.2 Hz, 1H), 7.88 (d, J = 8.9 Hz, 1H), 7.82 (d,
J = 7.8 Hz, 1H), 7.53 (m, 1H), 7.38–7.29 (m, 10H), 7.24 (d,
J = 8.0 Hz, 1H), 7.04 (d, J = 8.7 Hz, 1H), 5.16 (d, J = 12.1 Hz, 2H),
5.13 (br s, 1H), 5.08 (br s, 1H), 2.69–2.63 (m, 2H), 2.35 (m, 1H),
2.28 (m, 1H), 2.01–1.91 (m, 2H); 13C NMR (100 MHz, CDCl3) d
170.2, 155.2, 151.7, 147.9, 133.3, 133.2, 132.4, 130.9, 130.4,
128.8, 128.61, 128.56, 128.4, 128.31, 128.28, 128.04, 127.97,
127.5, 126.9, 126.4, 125.6, 124.5, 123.7, 122.7, 121.6, 118.2,
113.7, 68.1, 67.1, 38.6, 37.5, 28.2; FAB(+)HRMS Calcd for
4.2.2. 3-(Benzyloxycarbonylamino)tetrahydrothiophene-3-carb-
oxylic acid ( )-3
At first, 1.1 M aqueous NaOH (33 mL, 36.3 mmol) was added to
a stirred solution of 2 (1.53 g, 8.90 mmol) in MeOH (25 mL). After
stirring at 150 °C in a sealed tube for 24 h, the solution was diluted
with 1 M aqueous HCl and evaporated in vacuo to give the crude
amino acid 2. N-(Benzyloxycarbonyloxy)succinimide (Cbz-OSu,
3.59 g, 14.4 mmol) and Na2CO3 (1.24 g, 11.7 mmol) were then
added to a stirred solution of the crude amino acid in H2O
(50 mL) and THF (50 mL). After being stirred at room temperature
for 5 d, the THF was evaporated and the solution was washed with
n-hexane. The solution was acidified with 1 M aqueous HCl, ex-
tracted with EtOAc, and dried over MgSO4. Removal of the solvent
afforded crude ( )-3 (2.51 g, >99%), which was used for the next
reaction without further purification.
C
33H28NO5S (M++H) 550.1688, found 550.1707.
4.2.5. (S)-3-(Benzyloxycarbonylamino)tetrahydrothiophene-3-
carboxylic acid (ꢀ)-3 [Cbz-(S)-At5c]
At first, 1.1 M aqueous NaOH (10 mL) was added to a solution
of less polar-5 (352 mg, 0.64 mmol) in MeOH (5 mL) at 0 °C, and
the solution was then stirred at room temperature for 1 d. Next,
the solution was acidified with 1.1 M aqueous HCl, and the MeOH
was evaporated. The solution was extracted with EtOAC, and
dried over Na2SO4. Removal of the solvent afforded a residue,
which was purified by column chromatography on silica gel
(EtOAc) to give (ꢀ)-3 (171 mg, 95%) as colorless crystals. Mp
4.2.3. 3-(tert-Butoxycarbonylamino)tetrahydrothiophene-3-
carboxylic acid ( )-4
At first, 1.1 M aqueous NaOH (28 mL, 30.2 mmol) was added to
a stirred solution of 2 (1.13 g, 6.57 mmol) in MeOH (21 mL). After
stirring at 150 °C in a sealed tube for 15 h, the solution was diluted
148–150 °C; ½a 2D6
ꢁ
¼ ꢀ3:4 (c 1.00, MeOH); IR (KBr) 3391, 3375,
3067, 3038, 2980, 2945, 1744, 1670, 1533 cmꢀ1
;
1H NMR