Preparation of optically active allothreonine by separating from a diastereoisomeric mixture with threonine

Article abstract of DOI:10.1271/bbb.100295

A simple procedure is described to obtain D-and L-allothreonine (D-and L-aThr). A mixture of N-acetyl-D-allothreonine (Ac-D-aThr) and N-acetyl-L-threonine (Ac-L-Thr) was converted to a mixture of their ammonium salts and then treated with ethanol to precipitate ammonium N-acetyl-L- threoninate (Ac-L-Thr.NH3) as the less-soluble diastereoisomeric salt. After separating Ac-L-Thr.NH3 by filtration, Ac-D-aThr obtained from the filtrate was hydrolyzed in hydrochloric acid to give D-aThr of 80% de, recrystallized from water to give D-aThr of >99% de. L-aThr was obtained from a mixture of the ammonium salts of Ac-L-aThr and Ac-D-Thr in a similar manner.

Full text of DOI:10.1271/bbb.100295

Biosci. Biotechnol. Biochem., 74 (10), 2106–2109, 2010
Note
Preparation of Optically Active Allothreonine by Separating
from a Diastereoisomeric Mixture with Threonine
y
Tatsuo YAJIMA, Serina ICHIMURA, Shirabe HORII, and Tadashi SHIRAIWA
Faculty of Chemistry, Materials and Bioengineering, Kansai University, Yamate-cho, Suita, Osaka 564-8680, Japan
Received April 19, 2010; Accepted June 30, 2010; Online Publication, October 7, 2010
[doi:10.1271/bbb.100295]
A simple procedure is described to obtain D- and
L-allothreonine (D- and L-aThr). A mixture of N-acetyl-
D-allothreonine (Ac-D-aThr) and N-acetyl-L-threonine
(Ac-L-Thr) was converted to a mixture of their ammo-
nium salts and then treated with ethanol to precipitate
crystallization seemed to be a simple and efficient
procedure. However, such optical resolution would
require an optically active compound such as a resolving
6
)
agent in separating the diastereoisomeric salts, seed
7
)
crystals in preferential crystallization, and an optically
8
)
.
ammonium N-acetyl-L-threoninate (Ac-L-Thr NH3) as
the less-soluble diastereoisomeric salt. After separating
active cosolute in replacing crystallization. We have
already reported the preparation of aThr by replacing
8
)
.
Ac-L-Thr NH3 by filtration, Ac-D-aThr obtained from
crystallization with alanine as a cosolute. We report in
the present work a procedure to obtain D- and L-aThr
from diastereoisomeric mixtures of Thr and aThr, which
were given by epimerizing Thr, by a simpler and more
efficient procedure without employing such a chiral
factor as alanine.
the filtrate was hydrolyzed in hydrochloric acid to give
D-aThr of 80% de, recrystallized from water to give
D-aThr of >99% de. L-aThr was obtained from a
mixture of the ammonium salts of Ac-L-aThr and
Ac-D-Thr in a similar manner.
Optically active ꢀ-amino acids undergo racemization
or epimerization at the C-2 position with carbonyl
Key words: allothreonine;
threonine;
N-acetylated
1
1)
derivative; separation of diastereoisomeric
ammonium salts
compounds as a catalyst in carboxylic acid. L-Thr
was subjected to epimerization by stirring in acetic
ꢀ
acid at 90 C for 4 h, using salicylaldehyde as the
catalyst, to give a diastereoisomeric mixture of L-Thr
L- and D-Allothreonines ((2S,3S)- and (2R,3R)-2-
amino-3-hydroxybutanoic acids; L- and D-aThr) are
non-proteinogenic ꢀ-amino acids and diastereoisomers
of L-threonine ((2S,3R)-2-amino-3-hydroxybutanoic
acid; L-Thr), a normal constituent of proteins, and are
difficult to obtain in large quantities. D-aThr has been
identified as a constituent of the Hafnia alvei strain PCM
8
)
and D-aThr in a molar ratio of 1:0.7; the molar ratio
of L-Thr and D-aThr in the mixture was determined by
the intensity ratio of the methine proton signals at the
1
C-2 positions in the H-NMR spectrum of the mixture,
the signals for L-Thr and D-aThr respectively appearing
at 3.57 and 3.83 ppm. The epimerization of D-Thr also
gave a mixture of D-Thr and L-aThr in a molar ratio of
1
)
1
stituent of such cyclic peptides as coibamide A and
206 lipopolysaccharide. L-aThr is an important con-
2
)
1:0.7. As L-Thr is more soluble than D-aThr in
3)
8,12)
lysobactin, displaying very strong antibacterial activity
against methicillin-resistant Staphylococcus aureus. In
addition, D- and L-aThr serve as useful chiral building
blocks in asymmetric syntheses.4 D- and L-aThr have
water,
we first attempted to separate aThr from
the diastereoisomeric mixtures by recrystallizing from
water. However, separation seemed to be difficult even
8,13)
by repeated recrystallization.
We next attempted to separate aThr by transforming
the mixture into a simple derivative. Optical resolution
by separating diastereoisomers generally gives the
enantiomer with higher optical purity from the less-
)
5
)
been obtained by an asymmetric synthesis, optical
6
–8)
resolution of DL-aThr,
enzymatic resolution of
9
)
N-acylated and O-methylated DL-aThr, and selective
enzymatic hydrolysis of a mixture of N-acetylated and
O-benzylated L-Thr and D-aThr. Of these methods,
optical resolution by separating the diastereoisomers by
1
0)
soluble
(Ac-L-aThr) has been reported to have a higher melting
diastereoisomer.
N-Acetyl-L-allothreonine
ꢀ
9)
point (mp 153–154 C) than N-acetyl-L-threonine
10)
ꢀ
(
Ac-L-Thr; mp 118–119 C). Since the solubility and
R1
L-Thr NH2
L-aThr NH2
R2 R3 R4
melting point are correlated to some extent, the levels of
solubility of Ac-D- and -L-aThr were expected to be
lower than those of Ac-D- and -L-Thr. A mixture
R4
R3
H
H
OH
H
H
OH
OH
H
COOH
(50.0 mmol) containing 3.51 g of L-Thr and 2.45 g of
R2
R1
D-aThr, which had been obtained by epimerizing L-Thr
with salicylaldehyde in acetic acid, was allowed to react
with acetic anhydride in acetic acid to give an
N-acetylated mixture as an oily substance, but attempts
D-Thr
H
H
NH2
H
2-Amino-3-hydroxybutanoic acids
D-aThr
NH2 OH
y
To whom correspondence should be addressed. Fax: +81-6-6330-3770; E-mail: t.yajima@kansai-u.ac.jp
.
Abbreviations: aThr, allothreonine; Thr, threonine; Ac-D-aThr, N-acetyl-D-allothreonine; Ac-L-Thr, N-acetyl-L-threonine; Ac-D-aThr NH3,
.
ammonium N-acetyl-D-allothreoninate; Ac-L-Thr NH3, ammonium N-acetyl-L-threoninate

Preparation of Optically Active Allothreonine
2107
to crystallize the N-acetylated mixture were unsuccessful.
N-Acetylated amino acids tend to form good crys-
talline ammonium salts; for example, the ammonium
salts of N-acetyl-D-alloisoleucine and N-acetyl-L-iso-
lected by filtration in a yield of 72.7%. On the other
hand, the filtrate was evaporated in vacuo to give a
.
.
mixture of Ac-L-Thr NH3 and Ac-D-aThr NH3 as an
oily residue. After hydrolyzing the mixture in hydro-
chloric acid and then evaporating to dryness in vacuo,
an ethanol solution of the residue was treated with
triethylamine to precipitate D-aThr of 80% de in a yield
of 1.92 g; the diastereoisomeric excess of D-aThr was
determined by the intensity ratio of the methine proton
signals at the C-2 positions of aThr and Thr in the
leucine can be separated from their mixture by
recrystallization.1
4,15)
The networks of hydrogen bonds
with the ammonium ions in the crystals of these
ammonium salts determine the rigidity of the crystal
packing, so that a difference in the side chain
conformation of the amino acids would greatly affect
their solubility. An ammoniacal aqueous solution of a
mixture of Ac-L-Thr and Ac-D-aThr was evaporated to
dryness in vacuo to give a mixture of the ammonium
1
H-NMR spectrum. This crude D-aThr was recrystal-
lized from water-ethanol to give diastereoisomerically
pure D-aThr in a yield of 49.0% (1.20 g). On the other
hand, a mixture of D-Thr and L-aThr (50.0 mmol) was
treated in a manner similar to give L-aThr of >99% de
in a yield of 48.2% (1.18 g). D-aThr and L-aThr of
.
salts of Ac-L-Thr and Ac-D-aThr (Ac-L-Thr NH3 and
.
Ac-D-aThr NH ) as a viscous residue, this giving a
white solid after adding 2-propanol. The H-NMR
3
1
1
spectrum of the white solid exhibited the presence of
>99% de were determined from the H-NMR spectra.
.
.
The structure of Ac-L-Thr NH (Fig. 1), which had
was investigated in detail
only Ac-L-Thr, indicating that all of Ac-D-aThr NH
3
3
1
6)
remained in the 2-propanol solution. The crystals
obtained by recrystallizing the solid from ethanol were
determined by an X-ray crystal structure analysis to be
already been reported,
concerning the intermolecular hydrogen bonds
(Table 1). The O(1) atom of the carboxylate group of
the Ac-L-Thr ion interacted with the hydroxyl group of
.
Ac-L-Thr NH3, whose crystal structure had already
16)
˚
.
been reported.
Ac-L-Thr NH3 was recovered from
the suspension in 2-propanol in a yield of 63.4%, this
being calculated on the basis of the amount of L-Thr
another Ac-L-Thr ion (H(3)ꢂ ꢂ ꢂO(1) = 1.88 A) and an
˚
ammonium ion (H(12)ꢂ ꢂ ꢂO(1) = 1.89 A) more strongly
than the O(2) atom, which interacted with two other
˚
ammonium ions (1.94 and 1.93 A). This is consistent
with the electronic imbalance inferred from the differ-
(
3.51 g) in the starting mixture (5.96 g, 50.0 mmol). The
.
gathered Ac-L-Thr NH gave optically pure Ac-L-Thr,
3
2
D
0
17)
20
D
˚
ence in bond length between C(1)–O(1) (1.2626(12) A)
exhibiting ½ꢀꢁ þ12:4 (c 4.84, CH OH) (lit. ½ꢀꢁ
3
˚
and C(1)–O(2) (1.2517(14) A) of the carboxylate
þ12 (c 4.7, CH OH)), after adding HCl aq., suggesting
3
that L-Thr had not been racemized in the procedure
.
group. The fourth N–H bond of the ammonium ion
interacted strongly with the C=O moiety of an acetyl
for obtaining Ac-D-aThr NH3. After collecting
.
.
˚
Ac-L-Thr NH3 by filtration, Ac-D-aThr NH3 was al-
lowed to precipitate by cooling the filtrate in a yield of
group (H(11)ꢂ ꢂ ꢂO(4) = 1.87 A), indicating that this
C=O moiety was more polarized in comparison with
the carboxyl group. It seems to have made
4
1.4%, this being calculated on the basis of the amount
.
of D-aThr (2.45 g) in the same starting mixture. The
filtrate was calculated to contain approximately a 1:1
Ac-L-Thr NH3 less soluble that an Ac-L-Thr ion
interacted with the other Ac-L-Thr ions with two
strong hydrogen bonds and with ammonium ions with
.
.
mixture of Ac-L-Thr NH3 (1.92 g) and Ac-D-aThr NH3
2.15 g). It seemed to be difficult to obtain further
(
Ac-D-aThr NH from the 2-propanol filtrate by recrys-
.
tallization, because the respective solubility of
3
.
.
Ac-L-Thr NH and Ac-D-aThr NH was 0.074 g and
H(3)
O(3)
3
3
3
ꢀ
0
.174 g in 100 cm of 2-propanol at 25 C.
.
The respective solubility of Ac-L-Thr NH3 and
Ac-D-aThr NH3 in 100 cm of ethanol at 20 C was
.240 g and 1.474 g, indicating that Ac-D-aThr NH3 was
about 6 times more soluble than Ac-L-Thr NH3. These
results implied that Ac-L-Thr NH3 and Ac-D-aThr NH3
might be more efficiently separated by using ethanol
rather than 2-propanol as the solvent. After adding
3
ꢀ
C(3)
H(7)
.
.
0
H(14)
C(2)
.
N(1)
H(12)
.
.
O(4)
N(2)
H(11)
H(13)
O(1)
O(2)
.
ethanol to the viscous mixture of Ac-L-Thr NH and
3
.
.
Fig. 1. ORTEP View of Ac-L-Thr
NH3.
.
Ac-D-aThr NH , precipitated Ac-L-Thr NH was col-
3
3
˚
Table 1. Distances (A) and Angles ( ) for Hydrogen Bonds of Ac-L-Thr NH3
ꢀ
.
D–Hꢂ ꢂ ꢂA
O(3)–H(3)ꢂ ꢂ ꢂO(1)
N(1)–H(7)ꢂ ꢂ ꢂO(3)
Dꢂ ꢂ ꢂA
D–H
Hꢂ ꢂ ꢂA
D–Hꢂ ꢂ ꢂA
a
a
2.6719(12)
2.8912(12)
2.7711(13)
2.8382(14)
3.2496(14)
3.3113(14)
2.8265(14)
2.8339(14)
0.821(16)
0.895(13)
0.919(14)
0.957(17)
0.957(17)
0.914(14)
0.914(14)
0.919(18)
1.881(16)
1.998(13)
1.869(14)
1.892(17)
2.752(15)
2.560(15)
1.940(14)
1.926(18)
161.4(16)
175.5(14)
166.7(12)
169.4(14)
113.1(11)
139.7(12)
162.8(13)
169.0(16)
N(2)–H(11)ꢂ ꢂ ꢂO(4)
N(2)–H(12)ꢂ ꢂ ꢂO(1)
N(2)–H(12)ꢂ ꢂ ꢂO(3)
N(2)–H(13)ꢂ ꢂ ꢂO(1)
N(2)–H(13)ꢂ ꢂ ꢂO(2)
N(2)–H(14)ꢂ ꢂ ꢂO(2)
b
c
d
d
e
Symmetry operations: a) ꢃ1=2 þ x, 1=2 ꢃ y, 1 ꢃ z; b) 2 ꢃ x, 1=2 þ y, 1=2 ꢃ z; c) 3=2 ꢃ x, 1 ꢃ y, ꢃ1=2 þ z; d) 3=2 þ x, ꢃy, ꢃ1=2 þ z; e) 1 ꢃ x, 1=2 þ y, 1=2 ꢃ z

2
108
T. YAJIMA et al.
collected by filtration, washed with methanol, and dried. L-aThr of
99% de was prepared from the mixture (50 mmol) of L-Thr and
D-aThr in a manner similar to that for D-aThr.
some hydrogen bonds involving the carboxylate groups
and the amide C=O group.
>
The method reported in this paper is simpler and more
efficient than that already reported and might be suitable
for producing aThr on an industrial scale because of
the easy preparation which does not require another
chiral reagent.
2
0
ꢃ3
D-aThr. Yield, 1.20 g; ½ꢀꢁ ꢃ31:3 (c 1.00, 5 mol dm
HCl).
H-NMR (400 MHz, D2O, DSS) ꢁ: 4.39–4.32 (1H, m, 3-CH), 3.83 (1H,
D
1
d, 2-CH), 1.19 (3H, d, 4-CH3).
L-aThr. Yield, 1.18 g; ½ꢀꢁ þ31:8 (c 1.00, 5 mol dm HCl) (ref.18)
2
0
ꢃ3
D
2
D
0
ꢃ3
1
½ꢀꢁ þ31:7 (5 mol dm HCl)). The H-NMR spectrum was virtually
identical to that of D-aThr.
.
.
Experimental
General. Specific rotation data were collected at 589 nm and 20 C
Solubility. Ac-L-Thr NH3 (1.843 g) or Ac-D-aThr NH3 (2.563 g)
ꢀ
3
ꢀ
was dissolved in 25 cm of 2-propanol at 50 C. After vigorously
ꢀ
.
stirring the solution for 24 h at 25 C, the precipitated Ac-L-Thr NH3
or Ac-D-aThr NH3 was rapidly collected by filtration and thoroughly
with a Horiba Seisakusho SEPA-300 auto-polarimeter equipped with a
1
.
quartz cell with a 10.0-cm path length. H-NMR spectra were recorded
by a Jeol JNM-AL400 FT NMR system in deuterium oxide with sodium
ꢀ
dried. The solubility at 25 C was calculated on the basis of the weight
.
.
.
3
-(trimethylsilyl)propane-1-sulfonate (DSS) as an internal standard.
of Ac-L-Thr NH3 or Ac-D-aThr NH3. The solubility of Ac-L-Thr NH3
.
ꢀ
Chemical shift values are reported in ꢁ units downfield from DSS.
L- and D-Thr were purchased from Wako Pure Chemical Industries.
Epimerization of L- and D-threonine. L-Thr (23.8 g, 200 mmol) was
and Ac-D-aThr NH3 in ethanol at 20 C was measured in a manner
similar to that just described.
.
X-Ray crystallography. The X-ray experiment for Ac-L-Thr NH3
was carried out with a Rigaku RAXIS imaging plate area detector with
3
ꢀ
dissolved in 400 cm of acetic acid at 90 C. After adding salicylalde-
hyde (2.44 g, 20.0 mmol) to the solution, the mixture was stirred for 2 h
˚
graphite-monochromated MoKꢀ radiation (ꢂ ¼ 0:71070 A). The crys-
ꢀ
ꢀ
ꢀ
at 90 C. The mixture was then concentrated in vacuo at 60 C to give a
mixture of L-Thr and D-aThr as the diastereoisomeric residue. After
tal was mounted on a nylon loop at ꢃ150 C. To determine the cell
constant and orientation matrix, three oscillation photographs were
ꢀ
3
adding 400 cm of methanol to this residue and then stirring for 0.5 h at
ꢀ
taken for each frame with an oscillation angle of 3 and exposure time
4
0 C, the mixture was collected by filtration, washed thoroughly with
of 30 s. Intensity data were collected from the oscillation photographs,
and the reflection data were corrected for Lorentz and polarization
effects. The structure was solved by the direct method19) and expanded
by the Fourier technique.20) Non-hydrogen atoms were refined
anisotropically by a full-matrix least-squares calculation. Hydrogen
atoms were found from the difference Fourier map and isotropically
refined. All calculations were performed by using the CrystalStruc-
ture21) and Crystals22) crystallographic software packages. Crystallo-
graphic data: C6H14O4N2, M ¼ 178:19, orthorhombic, P212121, a ¼
methanol, and dried. The molar ratio of L-Thr and D-aThr in the
mixture was determined by the intensity ratio of the methine proton
signals at the C-2 positions in the 1H-NMR spectrum of the mixture.
Epimerization of D-Thr (23.8 g, 200 mmol) was carried out in a manner
similar to that for L-Thr. The mixtures were composed of Thr and
2
D
0
aThr in a molar ratio of 1:0.70 with a yield of 16.4 g and ½ꢀꢁ ꢃ22:1
ꢃ3
(
c 1.00, 1 mol dm HCl) for the mixture of L-Thr and D-aThr, and with
20
a yield of 11.4 g and ½ꢀꢁ þ22:0 (c 1.00, 1 mol dmꢃ3 HCl) for the
D
˚
˚
˚
˚ 3
mixture of D-Thr and L-aThr.
7:0136ð7Þ A, b ¼ 8:0869ð8Þ A, c ¼ 16:7882ð15Þ A, V ¼ 952:20ð16Þ A ,
ꢃ3
Preparation of ammonium N-acetyl-L-threonine and ammonium
N-acetyl-D-allothreonine. The diastereoisomeric mixture, which was
composed of L-Thr and D-aThr in a molar ratio of 1:0.7, (5.96 g,
Z ¼ 4, Dcalc ¼ 1:243 g cm , 2176 unique reflections. Refinement with
all 9335 reflection converged at final R ¼ 0:0323 and wR2 ¼ 0:0595;
CCDC 779488.
3
50.0 mmol) was dissolved in 50 cm of acetic acid. After adding acetic
anhydride (6 cm , 63.5 mmol) dropwise to the solution and stirring for
3
Acknowledgments
ꢀ
0
.5 h at 90 C, the mixture was evaporated in vacuo. To a solution of
the residue in 50 cm3 of water was added concentrated aqueous
This research study was financially supported in part
by grant-aid for encouragement of scientists from
Kansai University Research Grants, 2010.
3
ammonia. After evaporating the mixture in vacuo, 50 cm of
.
2-propanol was added to the residue. The precipitated Ac-L-Thr NH3
was collected by filtration, washed with a small amount of cold
2-propanol, and dried. The filtrate was solidified by stirring for 15 min
in an ice bath, and then 25 cm3 of 2-propanol was added to the
resulting solid. After the solid had been finely broken up in an
References
.
ultrasonic cleaner while cooling, Ac-D-aThr NH3 was collected by
filtration, washed with a small amount of cold 2-propanol, and dried.
1) Petersson C, Niedziela T, Jachymek W, Kenne L, Zarzecki P,
and Lugowski C, Eur. J. Biochem., 244, 580–586 (1997).
2) Medina RA, Goeger DE, Hills P, Mooberry SL, Huang N,
Romero LI, Ortega-Barria E, Gerwick WH, and McPhail KL,
J. Am. Chem. Soc., 130, 6324–6325 (2008).
.
ꢀ
20
Ac-L-Thr NH3. Yield, 3.32 g; mp 152–154 C (decomp.); ½ꢀꢁ
D
1
þ28:4 (c 1.00, methanol). H-NMR (400 MHz, D2O, DSS) ꢁ: 4.27–
4
.20 (1H, m, 3-CH), 4.14 (1H, d, 2-CH), 2.07 (3H, s, –NHCOCH3),
.17 (3H, d, 4-CH3). Anal. Calcd. for C6H14N2O4: C, 40.44; H, 7.92;
1
N, 15.72%. Found: C, 40.38; H, 7.63; N, 15.58%.
3) Guzman-Martinez A, Lamer R, and VanNieuwenhze MS, J.
Am. Chem. Soc., 129, 6017–6021 (2007).
.
ꢀ
20
D
Ac-D-aThr NH3. Yield, 1.52 g; mp 151–153 C (decomp.); ½ꢀꢁ
4) Coppola GM and Schuster HF, ‘‘Asymmetric Synthesis,’’ John
Wiley & Sons, New York, pp. 163–166 (1987).
5) Li Q, Yang S-B, Zhang Z, Li L, and Xu P-F, J. Org. Chem., 74,
1627–1631 (2009).
1
ꢃ16:2 (c 1.00, methanol). H-NMR (400 MHz, D2O, DSS) ꢁ: 4.39 (1H,
d, 2-CH), 4.28–4.18 (1H, m, 3-CH), 2.06 (3H, s, –NHCOCH3), 1.14
(3H, d, 4-CH3). Anal. Calcd. for C6H14N2O4: C, 40.44; H, 7.92; N,
1
5.72%. Found: C, 40.52; H, 7.69; N, 15.56%.
6) Arold H, J. Prakt. Chem., 24, 23–26 (1964).
7) Miyazaki H, Morita H, Shiraiwa T, and Kurokawa H, Bull.
Chem. Soc. Jpn., 67, 1899–1903 (1994).
Preparation of D- and L-allothreonine. A mixture of L-Thr and
D-aThr (5.96 g, 50.0 mmol) was acetylated, and then concentrated
.
aqueous ammonia added to give a mixture of Ac-L-Thr NH3 and
8) Shiraiwa T, Fukuda K, and Kubo M, Chem. Pharm. Bull., 50,
287–291 (2002).
.
Ac-D-aThr NH3, in a manner similar to that just described. To the
3
.
mixture was added 50 cm of ethanol. The precipitated Ac-L-Thr NH3
was collected by filtration, washed with a small amount of cold
ethanol, and dried. After evaporating the filtrate in vacuo and then
9) Winitz M, Bloch-Frankenthal L, Izumiya N, Birnbaum SM,
Baker CG, and Greenstein JP, J. Am. Chem. Soc., 78, 2423–
2430 (1956).
refluxing a solution of the residue in 65 cm3 of 5 mol dm hydro-
chloric acid for 2 h, the solution was evaporated in vacuo. To the
residue was added 50 cm3 of ethanol. After removing ammonium
chloride by filtration, the filtrate was adjusted to pH 6 with trieth-
ylamine. The precipitated D-aThr of 80% de was collected by filtration,
ꢃ3
10) Lloyd-Williams P, Sanchez A, Carulla N, Ochoa T, and Giralt
E, Tetrahedron, 53, 3369–3382 (1997).
11) Yamada S, Hongo C, Yoshioka R, and Chibata I, J. Org. Chem.,
48, 843–846 (1983).
12) Shiraiwa T, Kubo M, Fukuda K, and Kurokawa H, Biosci.
Biotechnol. Biochem., 63, 2212–2215 (1999).
3
washed with ethanol, and dried, yielding 1.92 g. After adding 40 cm of
3
ethanol to a solution of the crude D-aThr in 25 cm of water and then
stirring for 30 min at room temperature, D-aThr of >99% de was
13) Sato M, Okawa K, and Akabori S, Bull. Chem. Soc. Jpn., 30,
937–938 (1957).

Preparation of Optically Active Allothreonine
2109
1
4) Yajima T, Horikawa T, Takeda N, Takemura E, Hattori H,
Shimazaki Y, and Shiraiwa T, Tetrahedron: Asymmetry, 19,
19) Altomare A, Cascarano G, Giacovazzo C, Guagliardi A, Burla
MC, Polidori G, and Camalli M, J. Appl. Cryst., 27, 435 (1994).
20) Beurskens PT, Admiraa G, Beurskens G, Bosma WP, de Gelder
R, Israel R, and Smits JMM, The DIRDIF-99 program system,
Technical Report of the Crystallography Laboratory, University
of Nijmegen, The Netherlands, 1999.
1285–1287 (2008).
1
5) Yajima T, Kimura M, Nakakoji M, Horikawa T, Tokuyama Y,
and Shiraiwa T, Biosci. Biotechnol. Biochem., 73, 2293–2298
(
2009).
6) Puliti R and Mattia CA, Acta Crystallogr. C, 56, 496–499
2000).
1
1
1
21) Crystal Structure Analysis Package, Rigaku and Rigaku
Americas, 9009 New Trails DR. The Woodlands TX 77381
USA, 2000–2007.
(
7) Cardillo G, Gentilucci L, Tolomelli A, and Tomasini C,
Tetrahedron Lett., 38, 6953–6956 (1997).
22) Carruthers JR, Rollett JS, Betteridge PW, Kinna D, Pearce L,
Larsen A, and Gabe E, Chemical Crystallography Laboratory,
Oxford, UK, 1999.
8) Otey MC, Greenstein JP, Winitz M, and Birnbaum SM, J. Am.
Chem. Soc.,77, 3112–3114 (1955).