A short, versatile chemical synthesis of L- And D-amino acids stereoselectively labelled solely in the beta position

Article abstract of DOI:10.1039/b508196c

L- and D-Amino acids which are stereoselectively labelled solely either in the 3-pro-R or in the 3-pro-S-positions have been prepared by a relatively short chemical synthesis in ee of 81 to 86%. This involves Sharpless' aminohydroxylation and cyclisation

Full text of DOI:10.1039/b508196c

View Online / Journal Homepage / Table of Contents for this issue
A R T I C L E
A short, versatile chemical synthesis of L- and D-amino acids
stereoselectively labelled solely in the beta position
Kreingkrai Lowpetch and Douglas W. Young*
Department of Chemistry, University of Sussex, Falmer, Brighton, UK BN1 9QJ
Received 10th June 2005, Accepted 5th July 2005
First published as an Advance Article on the web 15th August 2005
L- and D-Amino acids which are stereoselectively labelled solely either in the 3-pro-R or in the 3-pro-S-positions
have been prepared by a relatively short chemical synthesis in ee of 81 to 86%. This involves Sharpless’
aminohydroxylation and cyclisation with inversion of stereochemistry at C-2 to give the stereoselectively labelled
D- and L-aziridines 10a and 10b, and 8a and 8b. These have previously been modified and cleaved with inversion of
stereochemistry at C-3 using a number of nucleophiles to give a large variety of protected amino acids. Synthesis of
the labelled D- and L-b-chloroalanines 22a and 22b and 25a and 25b is described here.
Introduction
Results and discussion
Our understanding of the mechanism of action of enzymes
which metabolise amino acids has been greatly advanced by
elucidation of the stereochemical consequences of these enzymic
reactions.1 In most naturally-occurring amino acids, the b-
carbon atom is prochiral and so, to discover the stereochem-
ical consequences of reactions at this centre, stereospecifically
labelled substrates and products must be synthesised.1 We have
devised a chemico-enzymatic synthesis which is summarised in
part in Scheme 1. This has allowed a large variety of D- and
L-amino acids, 5 and 7, which are stereospecifically labelled
at the b-carbon to be prepared.2,3,4 Compounds prepared in
this way were used to study the stereochemistry of some of
the many enzyme catalysed reactions of amino acids.4–8 The
synthesis was lengthy, especially for the preparation of the
more commonly occurring L-amino acids 7.3 Further, it is
usual to carry out metabolic studies with epimerically labelled
substrates in tandem and so both possible isotopomers at C-3
of the appropriate amino acid are required. Although one
isotopomer was always obtained singly labelled at C-3 by our
chemico-enzymatic synthesis, the second isotopomer always
contained a second label at C-2 because of the symmetrical
nature of starting material 1 in the enzymic step (1 → 2).
While this does not prevent the stereochemical fate of many
metabolic reactions being elucidated by a combination of NMR
spectroscopy and synthetic studies,4–8 it has disadvantages when
the stereochemical consequences of a reaction need to be derived
using kinetic methods. In such cases, isotope effects from the a-
label might obscure the effect from the isotope on the b-atom.
We now wish to report an entirely chemical route to both D- and
L-amino acids which is relatively short and leads to both D- and
L-amino acids which are stereoselectively labelled solely on the
b-carbon atom.
The utility and versatility of the labelled aziridines 4 and 6 for
the preparation of a large variety of stereospecifically labelled
D- and L-amino acids 5 and 7 had been amply demonstrated in
our earlier chemico-enzymatic synthesis2,4 and so our aim was
to shorten the synthesis of these aziridines and to ensure that
they were labelled stereoselectively solely on the b-carbon atom.
Our proposed synthesis is shown retrosynthetically in Scheme 2,
where the singly labelled isoserine derivatives 9 and 11 (HA or
2
HB = H) might be prepared by Sharpless aminohydroxylation
of methyl (Z)- and (E)-[3-2H1]-acrylate, 12a and 12b respectively,
using an appropriate chiral catalyst.
Scheme 2
Methyl (Z)- and (E)-[3-2H1]-acrylate, 12a and 12b respectively,
were prepared from the corresponding labelled (Z)- and (E)-[3-
2H1]-acrylic acids 15a and 15b,9 which were prepared in turn
from (Z) and (E)-3-bromoacrylic acids 14a and 14b,10 as shown
in Scheme 3. Heating the acids 15a and 15b at 75 ◦C in methanol
containing a catalytic quantity of sulfuric acid gave the esters
12a and 12b in 46% and 40% yields respectively. The relatively
low yields were due in part to polymerisation on distillation and
the low boiling point of the esters.
Scheme 1
T h i s j o u r n a l i s
3 3 4 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

View Online
Scheme 3 Reagents and conditions: (i) ref. 10 (63% 14a, 72% 14b); (ii) ref. 9 (72% 15a, 75% 15b); (iii) MeOH/98% H2SO4/75 ◦C, 1.5 h
(46% 12a, 40% 12b); (iv) (a) PhCH2OCONH2/NaOH//tBuOCl, (b) 12/(DHQ)2PHAL/K2OsO2(OH)4/rt, ca. 1 h (67% 16, 82% 16a, 62% 16b);
(v) (a) PhCH2OCONH2/NaOH//tBuOCl, (b) 12/(DHQD)2PHAL/K2OsO2(OH)4/rt, ca. 1 h (60% 17, 81% 17a, 60% 17b); (vi) (R)-Mosher’s
acid/CH2Cl2/ PrN
N Pr/0 ◦C, then rt, 60 h (91% 18, 80% 18a, 77% 18b; 94% 19, 80% 19a, 85% 19b).
i
i
=
C
=
Scheme 4 Reagents and conditions: (i) H2/10% Pd–C/32% aq HCl/MeOH/rtp, 48 h (quant 11a, quant 11b); (ii) Ph3CCl/Et3N/CHCl3/0 ◦C,
4.5 h, then rt, 18 h (61% 20a, 72% 20b); (iii) NEt3/THF/MsCl rt 30 min then reflux 48 h (89% 10a, 60% 10b); (iv) (a) TFA/CHCl3 0 ◦C, 2.5 h,
(b) ClCO2CH2Ph/EtOAc/aq NaHCO3, 0 ◦C, then rt, 1.5 h (86% 21a, 98% 21b); (v) TiCl4/CHCl3/CH2Cl2 −78 ◦C, 16 h (80%); (vi) 4 M H2SO4
reflux, 3.5 h (57%).
Unlabelled methyl acrylate 12 and the labelled esters 12a
and 12b were now added in separate experiments together
with potassium osmate dihydrate to a solution of freshly
prepared BnOCONClNa11 in acetonitrile–water containing
1,3-phthalazinediyl-bis-dihydroquinine [(DHQ)2PHAL]. The
products were those of addition from the 2-re-face of
methyl acrylate, (2R)-, (2R,3R)-[3-2H1]- and (2R,3S)-[3-2H1]-
N-benzyloxycarbonylisoserinates, 16, 16a, and 16b respec-
tively. When the aminohydroxylation reaction was repeated
on the same substrates, but using 1,3-phthalazinediyl-bis-
dihydroquinidine [(DHQD)2PHAL] as the ligand, then the prod-
ucts of addition from the 2-si-face of the acrylate, (2S)-, (2S,3S)-
[3-2H1]- and (2S,3R)-[3-2H1]-N-benzyloxycarbonylisoserinates,
17, 17a and 17b respectively, were obtained. The specific
rotations of these compounds (Table 1) suggested that the
reactions were stereoselective and conversion into the esters 18,
18a and 18b, and 19, 19a and 19b of (R)-Mosher’s acid allowed
the enantiomeric excess (ee) for each product to be determined
using 19F NMR spectroscopy. In the 19F NMR spectra of the
(2R)-esters, 18, 18a and 18b, the major signal was at −71.7 ppm
and the minor signal was at −72.2 ppm from CFCl3, whilst in
the 19F NMR spectra of the (2S)-isomers 19, 19a and 19b, the
−71.7 ppm signal was the minor signal and −72.2 ppm was the
major signal. The ee for each reaction is also shown in Table 1.
Values of ee for the six reactions were reasonably consistent,
being between 81 and 86%.
Synthesis of the labelled D-aziridines 10 was now completed as
shown in Scheme 4 by first hydrogenolysing the (2S)-urethane-
esters 17a and 17b using hydrogen and 10% palladium on
charcoal in aqueous, methanolic hydrochloric acid to obtain
the methyl isoserinate hydrochlorides 11a and 11b in excellent
yields. These were then converted into the correspondingN-trityl
derivatives 20a and 20b using trityl chloride and triethylamine
◦
at 0 C. Cyclisation using mesyl chloride and triethylamine at
reflux then occurred with inversion of stereochemistry at C-2
1
to give the (2R)-aziridines 10a and 10b with H-NMR spectra
(Figs. 1d and 1e) in keeping with expectation from the spectra of
the products from our chemico-enzymatic synthesis2 (Figs. 1b
and 1c). Since we had already shown that these steps occurred
with one inversion and no loss of stereochemical integrity in our
chemico-enzymatic synthesis,2 the aziridines could be assumed
to have the same values for ee as the protected isoserines 16.
The specific rotations confirmed the absolute stereochemistry
of the labelled aziridines 10. Although the chemico-enzymatic
synthesis is evidently more stereoselective, the products 10a and
10b are suitable for metabolic studies where the (2S)-enantiomer
is not turned over by the enzyme (see following paper).
Synthesis of the labelled L-aziridines 8 is outlined in Scheme 5.
This involved the (2R)-isoserine derivatives 16a and 16b and used
the same chemistry as for the synthesis of the D-aziridines. Fig. 2
1
shows a comparison of the H NMR spectra of the products
(Figs. 2d and 2e) with the products of the chemico-enzymatic
synthesis3 (Figs. 2b and 2c). This, with the specific rotations,
again confirmed the absolute stereochemistry of the label.
Having improved the synthesis of the singly labelled (2R)-
and (2S)-N-tritylaziridine methyl esters, their conversion into
a large variety of appropriately labelled D- and L-amino acids
by removal of the trityl group and replacement with a more
electron-withdrawing group on nitrogen follows from our pre-
vious studies.2,4 When this group is urethane, then reaction with
halogen, sulfur and oxygen nucleophiles occurs with inversion of
stereochemistry to give the protected labelled amino acids.2 For
reaction with carbon nucleophiles, a sulfonamide is required
on nitrogen.4 The esters 10a/b and 8a/b were converted into
the corresponding samples of b-chloroalanine 22a/b and 25a/b
Table 1 Yields, specific rotations and eea of the compounds 16 and 17
Compound
Yield
[a]D
Eea
(2R) 16
67%
82%
62%
60%
81%
60%
−17.7
−15.6
−15.7
+18.2
+12.5
+12.2
81%
(2R,3R)-[3-2H1] 16a
(2R,3S)-[3-2H1] 16b
(2S) 17
85%
83%
86%
84%
85%
(2S,3S)-[3-2H1] 17a
(2S,3R)-[3-2H1] 17b
a Ee derived from 19F NMR spectrum of Mosher’s esters 18 and 19.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6
3 3 4 9

View Online
Scheme 5 Reagents and conditions: (i) H2/10% Pd–C/32% aq HCl/MeOH/rtp 48 h (quant 9a, quant 9b); (ii) Ph3CCl/Et3N/CHCl3/0 ◦C
4.5 h then rt 18 h (65% 23a, 57% 23b); (iii) NEt3/THF/MsCl rt 30 min then reflux 48 h (76% 8a, 61% 8b); (iv) (a) TFA/CHCl3
0
◦C, 2.5 h,
(b) ClCO2CH2Ph/EtOAc/aq NaHCO3, 0 ◦C, then rt, 1.5 h (95% 24a, 92% 24b); (v) TiCl4/CHCl3/CH2Cl2 −78 ◦C, 16 h (76%); (vi) 4 M H2SO4
reflux, 3.5 h (55%).
Fig. 2 Part of the 1H NMR spectra in C2HCl3 of (a) methyl
(2S)-N-tritylaziridine-2-carboxylate 6; (b) methyl (2S,3R)-[3-2H1]-N-
2
tritylaziridine-2-carboxylate 6 (HB = H) from the chemico-enzymatic
synthesis;3 (c) methyl (2S,3S)-[2,3-2H2]-N-tritylaziridine-2-carboxylate
6 (HA
=
2H) from the chemico-enzymatic synthesis;3 (d) methyl
(2S,3S)-[3-2H1]-N-tritylaziridine-2-carboxylate 8a from the chemical
synthesis; (e) methyl (2S,3R)-[3-2H1]-N-tritylaziridine-2-carboxylate 8b
from the chemical synthesis.
methods may be more easily used to probe stereochemical
aspects of the mechanism of enzyme catalysed reactions.
Fig. 1 Part of the 1H NMR spectra in C2HCl3 of (a) methyl
(2R)-N-tritylaziridine-2-carboxylate 4; (b) methyl (2R,3R)-[3-2H1]-N-
2
tritylaziridine-2-carboxylate 4 (HB = H) from the chemico-enzymatic
Experimental
synthesis;2 (c) methyl (2R,3S)-[2,3-2H2]-N-tritylaziridine-2-carboxylate
4 (HA
=
2H) from the chemico-enzymatic synthesis;2 (d) methyl
Melting points were determined using a Gallenkamp melting
point apparatus and are uncorrected. Optical rotations (in units
of 10−1 deg cm2 g−1) were measured using a Perkin Elmer
PE241 polarimeter with a 1 dm path length cell. IR spectra
were recorded using a Perkin Elmer 1710 Fourier transform
spectrometer. 1H-NMR spectra and 1H-decoupled-13C-NMR
spectra were recorded using a Bruker DPX 300 (300 MHz for
1H, 75.5 MHz for 13C) Fourier transform instrument. Residual
undeuteriated solvent peaks and tetramethylsilane (TMS) were
used as internal references for these spectra. 19F spectra were
recorded using a Bruker AMX 500 Fourier transform instru-
ment (376.4 MHz) with CFCl3 as internal standard. DEPT, 1H
COSY and 1H-13C COSY experiments were used to help assign-
ment of NMR spectra where required. Homonuclear decoupling
experiments were used to aid the determination of stereochem-
istry where necessary. NMR chemical shifts are given in ppm and
coupling constants (J) in Hz. All NMR spectra were recorded
at 25 ◦C. Mass spectra were obtained by Dr A. Abdul-Sada; low
resolution using Kratos MS 80RF (FAB), VG Autospec (EI)
or Bruker BioApex III (ESI) double focussing spectrometers;
high-resolution using a 4.7 FT-IRC (Bruker BioApex III)
spectrometer. Column chromatography was performed using
(2R,3S)-[3-2H1]-N-tritylaziridine-2-carboxylate 10a from the chemical
synthesis; (e) methyl (2R,3R)-[3-2H1]-N-tritylaziridine-2-carboxylate
10b from the chemical synthesis.
by the methods previously used in our chemico-enzymatic
synthesis.2 This is shown in Schemes 4 and 5 and described in
the experimental section. The 1H NMR spectra of the products
are shown in Figs. 3 and 4.
Conclusion
We have completed a general synthesis of D- and L-amino acids
stereoselectively labelled with one deuterium label on the b-
carbon atom. Although the synthesis is less stereoselective than
our chemico-enzymatic synthesis, it is much shorter and, since
the metabolic reactions which will be studied are stereospecific
for C-2, labelled amino acids prepared in this way should serve
as substrates with which to assess the stereoselectivity of a large
variety of enzymic reactions. This is exemplified in the work
reported in the following publication. The fact that all four
enantiotopically labelled substrates contain but a single label
is a distinct advantage over the previous synthesis, as kinetic
3 3 5 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6

View Online
Fig.
3
1H NMR spectrum in 10% 2HCl/2H2O of (a) (2S)-b-
chloroalanine; (b) (2S,3S)-[3-2H1]-b-chloroalanine 22b; and (c) (2S,3R)-
[3-2H1]-b-chloroalanine 22a.
Fig.
4
1H NMR spectrum in 10% 2HCl/2H2O of (a) (2R)-b-
chloroalanine; (b) (2R,3S)-[3-2H1]-b-chloroalanine 25a; and (c) (2R,3R)-
[3-2H1]-b-chloroalanine 25b.
R
Davisilꢀ Silica 60A, 35–70 mesh silica gel. Petroleum ether refers
to that fraction of hexanes of boiling point 60–80 ◦C.
6.40 (0.9H, d, J3Z,2 17.4, H-3), 6.13 (1H, d, J2,3Z 17.4, H-2), 5.83
(0.1H, d, J 10.2, H-3 of (Z)-isomer), 3.77 (3H, s, CH3), 3.66
(over-reduced product) and 2.29 (over-reduced product). Due
to the volatility of the product, it was used immediately in the
next step without further characterisation.
Methyl (Z)-[3-2H1]-acrylate (12a)
A solution of a mixture containing (Z)-[3-2H1]-acrylic acid 15a,9
a little over-reduced material, and some diethyl ether (3.48 g,
47.7 mmol) in methanol (1.98 g, 2.51 ml, 62.0 mmol) and 98%
sulfuric acid (90 mg, 0.9 mmol) was heated to an oil bath
temperature of 75 ◦C for 1.5 h and the mixture was left to cool.
The resulting light yellow solution was purified by fractional
distillation at atmospheric pressure using a 30 cm fractional
distillation column. The product methyl (Z)-[3-2H1]-acrylate 12a
(1.91 g, 46%) was collected at 70–80 ◦C as clear liquid containing
some diethyl ether, methanol and over-reduced product; m/z
[EI+] 88 [M + H]+; dH (300 MHz, C2HCl3) 6.12 (1H, m, H-2),
5.81 (1H, d, J3,2 10.5, H-3), 3.78 (3H, s, OCH3), 3.67 (over-
reduced product), 2.31 (over-reduced product) and 1.09 (over-
reduced product). Due to the volatility of the product, it was used
immediately in the next step without further characterisation.
The 1H NMR spectrum was in keeping with that of the
commercially available unlabelled methyl acrylate; dH (300 MHz,
C2HCl3) 6.42 (1H, d, J3,2 17.3, H-3E), 6.13 (1H, 2 × d, J2,3E 17.3,
J2,3Z 10.4, H-2), 5.84 (1H, d, J3,2 10.4, H-3Z) and 3.77 (3H, s,
OCH3).
Methyl (2R)-N-benzyloxycarbonylisoserinate (16)
A solution of sodium hydroxide (122 mg, 3.05 mmol) in water
(5 ml), followed by freshly prepared12 tert-butyl hypochlorite
(331 mg, 3.05 mmol) were added to a solution of benzyl
carbamate (486 mg, 3.1 mmol) in acetonitrile (4 ml). A solution
of (DHQ)2PHAL (40 mg, 0.05 mmol) in acetonitrile (3.5 ml)
and water (2.5 ml) was added and the mixture was stirred for
5 min at room temperature. Methyl acrylate 12 (86 mg, 1 mmol)
was added, followed by potassium osmate dihydrate (15 mg,
0.04 mmol). The mixture turned dark purple and gradually
became lighter. Stirring was continued at room temperature until
TLC indicated that the reaction was complete (ca. 50 min on
this scale). Ethyl acetate (7 ml) was added and the layers were
separated. The aqueous layer was washed with ethyl acetate (3 ×
10 ml). The combined organic layers were washed with brine
(10 ml) and water (10 ml), and dried (MgSO4). The solvent was
removed under reduced pressure to give an orange oil which was
purified by flash chromatography on silica gel using petroleum
ether–ethyl acetate (4 : 1) as eluent. The solvent was removed
from the fractions determined to be homogeneous by TLC
to yield methyl (2R)-N-benzyloxycarbonylisoserinate 16 as an
Methyl (E)-[3-2H1]-acrylate (12b)
This was prepared by the method described previously using (E)-
[3-2H1]-acrylic acid 15b9 (14.50 g, 0.20 mol), methanol (8.26 g,
0.26 mol) and 98% sulfuric acid (390 mg, 4 mmol). The product
methyl (E)-[3-2H1]-acrylate 12b (6.89 g, 40%) was obtained as
a clear liquid, containing diethyl ether, methanol and the over-
reduced product; m/z [EI+] 88 [M + H]+; dH (300 MHz, C2HCl3)
29
23
orange oil (170 mg, 67%); [a]D −17.7 (c 1.42, MeOH) (lit13 [a]D
+18.8 (c 1.42, MeOH) for (2S)-enantiomer); m/z (ES+) Found
276.0831, [C12H15NO5 + Na]+ requires 276.0842; mmax (film)/cm−1
3369 (OH) and 1724 (br, ester + urethane); dH (300 MHz,
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6
3 3 5 1

View Online
ligand. The product, methyl (2S,3R)-[3-2H1]-N-benzyloxycar-
C2HCl3) 7.32 (5H, br s, ArH), 5.10 (2H, s, OCH2Ph), 4.28 (1H,
br s, H-2), 3.78 (3H, s, OCH3) and 3.57 (2H, unresolved ABX,
H-3); dC (75.5 MHz, C2HCl3) 173.4 (ester), 157.0 (urethane),
136.6–128.5 (Ar), 70.429 (C-2), 67.4 (OCH2Ph), 53.3 (OCH3)
and 44.6 (C-3).
bonylisoserinate 17b (8.05 g, 60%) was obtained as an orange
27
oil; [a]D +12.20 (c 1.42, MeOH); m/z (ES+) Found 277.08999,
[C12H14NO5 H + Na]+ requires 277.09052; mmax (film)/cm−1 3373
2
(OH) and 1720 (br, ester + urethane); dH (300 MHz, C2HCl3)
7.31 (5H, s, ArH), 5.06 (2H, s, OCH2Ph), 4.27 (1H, d, J2,3S 5.3,
H-2), 3.71 (3H, s, OCH3) and 3.48 (1H, t, J3S,2 5.3, H-3S); dC
(75.5 MHz, C2HCl3) 173.8 (ester), 157.2 (urethane), 136.7–128.5
(Ar), 70.4 (C-2), 67.3 (OCH2Ph), 53.1 (OCH3) and 44.4 (t, JC,D
21, C-3).
Methyl (2R,3R)-[3-2H1]-N-benzyloxycarbonylisoserinate (16a)
This was prepared by the method described above using
freshly prepared impure methyl (Z)-[3-2H1]-acrylate 12a (2.98 g,
34 mmol), and (DHQ)2PHAL (1.33 g, 1.7 mmol) as the
ligand. The product, methyl (2R,3R)-[3-2H1]-N-benzyloxycar-
bonylisoserinate 16a (7.10 g, 82%) was obtained as an orange
Mosher’s ester (18) of methyl
(2R)-N-benzyloxycarbonylisoserinate
27
oil; [a]D −15.62 (c 1.42, MeOH); m/z (ES+) Found 277.0906,
[C12H14NO5 H + Na]+ requires 277.0905; mmax (film)/cm−1 3370
2
(R)-a-Methoxy-a-(trifluoromethyl)-phenylacetic acid (930 mg,
0.4 mmol), DMAP (24 mg, 0.2 mmol) and 1,3-diisopropyl-
carbodiimide (50 mg, 0.06 ml, 0.4 mmol) were added to
a solution of methyl (2R)-N-benzyloxycarbonylisoserinate 16
(50 mg, 0.2 mmol) in dichloromethane (0.5 ml) at 0 ◦C. The
mixture was left to warm to room temperature, and stirred for
60 h. Addition of diethyl ether (5 ml) gave a white precipitate
which was removed by filtration and washed with diethyl ether
(10 ml). The ether layer was washed with saturated aqueous
ammonium chloride (5 ml). The two phases were separated and
the aqueous phase was extracted with diethyl ether (3 × 5 ml).
The combined ether layers were washed with saturated aqueous
ammonium chloride (5 ml), water (5 ml) and brine (5 ml). The
solution was filtered and dried (MgSO4), and the solvent was
removed under reduced pressure. The resulting oil was purified
by flash chromatography on silica gel using petroleum ether–
ethyl acetate (4 : 1) as eluent. The solvent was removed from
the fractions determined to be homogeneous by TLC to give
(OH) and 1720 (br, ester + urethane); dH (300 MHz, C2HCl3)
7.33 (5H, br s, ArH), 5.08 (2H, s, OCH2Ph), 4.28 (1H, br s, H-2),
3.75 (3H, s, OCH3) and 3.56 (1H, br s, H-3S); dC (75.5 MHz,
C2HCl3) 173.8 (ester), 157.1 (urethane), 136.7–128.49 (Ar), 70.4
(C-2), 67.4 (OCH2Ph), 53.2 (OCH3) and 44.3 (t, JC,D 21, C-3).
Methyl (2R,3S)-[3-2H1]-N-benzyloxycarbonylisoserinate (16b)
This was prepared by the method described above using
freshly prepared impure methyl (E)-[3-2H1]-acrylate 12b (6.89 g,
79 mmol) and (DHQ)2PHAL (3.08 g, 4 mmol) as the
ligand. The product methyl (2R,3S)-[3-2H1]-N-benzyloxycar-
bonylisoserinate 16b (12.45 g, 62%) was obtained as an orange
35
oil; [a]D −15.76 (c 1.42, MeOH); m/z (ES+) Found 277.0907,
[C12H14NO5 H + Na]+ requires 277.0905; mmax (film)/cm−1 3367
2
(OH) and 1724 (br, ester + urethane); dH (300 MHz, C2HCl3)
7.33 (5H, s, ArH), 5.09 (2H, s, OCH2Ph), 4.28 (1H, br s, H-
2), 3.76 (3H, s, OCH3) and 3.51 (1H, d, J3R,2 5.0, H-3R); dC
(75.5 MHz, C2HCl3) 173.82 (ester), 157.1 (urethane), 136.7–
128.5 (Ar), 70.4 (C-2), 67.4 (OCH2Ph), 53.2 (OCH3) and 44.3 (t,
JC,D 20, C-3).
28
the product 18 (84 mg, 91%) as a clear oil; [a]D +23.82 (c
1, CHCl3); m/z (ES+) Found 492.1218, [C22H22NO7F3 + Na]+
requires 492.1240; mmax (film)/cm−1 3350 (OH), 1755 (ester) and
1732 (ester); dH (300 MHz, C2HCl3) 7.79 (2H, d, J 8, ArH),
7.17–7.02 (8H, m, ArH), 5.12 (1H, dd, J2,3R 6.3, J2,3S 4.5, H-2),
4.96 and 4.92 (2H, AB, JAB 12.3, OCH2Ph), 4.25 (1H, br, NH),
3.61 (3H, d, JH,F 1.2, OCH3), 3.21 (3H, s, OCH3) and 3.17 (2H,
m, H-3), [signals at 3.47 (OCH3) and 3.38 (m, H-3) were present
for ca. 14% of the (2S)-diastereoisomer]; dC (75.5, C2HCl3) 167.7
(ester), 166.3 (ester), 156.0 (urethane), 129.9–128.2 (Ar), 85.11
(q, JC,F 28.2, CF3) 73.0 (C-2), 66.9 (OCH2Ph), 55.8 (OCH3), 52.2
(OCH3) and 41.4 (C-3); dF (376.4 MHz, C2HCl3) −72.2 [0.28F, s,
(2S)-isomer] and −71.7 [2.72F, s, (2R)-isomer].
Methyl (2S)-N-benzyloxycarbonylisoserinate (17)
This was prepared by the method described above using
methyl acrylate 12 (86 mg, 1 mmol) and (DHQD)2PHAL
(40 mg, 0.05 mmol). The product, methyl (2S)-N-benzyloxycar-
bonylisoserinate 17 (153 mg, 60%) was obtained as an orange
oil; [a]D +18.2 (c 1.42, MeOH) (lit13 [a]D +18.8 (c 1.42,
MeOH); m/z (ES+) Found 276.0839, [C12H15NO5 + Na]+
requires 276.0842; mmax (film)/cm−1 3369 (OH) and 1724 (br,
ester + urethane); dH (300 MHz, C2HCl3) 7.33 (5H, br s, ArH),
5.08 (2H, s, OCH2Ph), 4.28 (1H, t, J2,3 4.5, H-2), 3.75 (3H, s,
OCH3) and 3.55 (2H, unresolved ABX, H-3); dC (75.5 MHz,
C2HCl3) 173.8 (ester), 157.1 (urethane), 136.7–128.5 (Ar), 70.5
(C-2), 67.4 (OCH2Ph), 53.2 (OCH3) and 44.6 (C-3).
30
23
Mosher’s ester (18a) of methyl (2R,3R)-[3-2H1]-N-
benzyloxycarbonylisoserinate
This was prepared by the method described above using methyl
(2R,3R)-[3-2H1]-N-benzyloxycarbonylisoserinate 16a (50 mg,
0.2 mmol). The product 18a (75 mg, 80%) was obtained as
Methyl (2S,3S)-[3-2H1]-N-benzyloxycarbonylisoserinate (17a)
32
a clear oil; [a]D +30.72 (c 1, CHCl3); m/z [ES+] Found
493.1293, [C22H21NO7F3 H + Na]+ requires 493.1303; mmax 3349
2
This was prepared by the method described previously using
freshly prepared impure methyl (Z)-[3-2H1]-acrylate 12a (2.48 g,
290 mmol) and (DHQD)2PHAL (1.11 g, 1.4 mmol) as the
ligand. The product, methyl (2S,3S)-[3-2H1]-N-benzyloxycar-
bonylisoserinate 17a (5.90 g, 81%) was obtained as an orange
(film)/cm−1 (OH), 1755 (ester) and 1732 (ester); dH (300 MHz,
C2HCl3) 7.79 (2H, d, J 8, ArH), 7.17–7.01 (8H, m, ArH), 5.14
(1H, d, J2,3 4.1, H-2), 4.96 and 4.92 (2H, AB, JAB 12.4, OCH2Ph),
4.42 (1H, d, J 6.2, NH), 3.61 (3H, d, JH,F 1.0, OCH3), 3.23 (3H, s,
OCH3) and 3.19 (1H, d, J3S,2 4.1, H-3S), a signal was present at
3.39 for OCH3 of the (2S)-isomer; dC (75.5 MHz, C2HCl3) 167.8
(ester), 166.3 (ester), 156.0 (urethane), 129.9–127.5 (Ar), 85.1 (q,
JC,F 27.8, CF3), 72.9 (C-2), 66.9 (OCH2Ph), 55.8 (OCH3), 52.3
(OCH3) and 41.2 (t, JC,D 22, C-3); dF (376.4 MHz, C2HCl3) −72.2
[0.225F, s, (2S)-isomers] and −71.7 [2.775F, s, (2R)-isomers].
30
oil; [a]D +12.5 (c 1.42, MeOH); m/z (ES+) Found 277.08945,
[C12H14NO5 H + Na]+ requires 277.09052; mmax (film)/cm−1 3372
2
(OH) and 1723 (br, ester + urethane); dH (300 MHz, C2HCl3)
7.31 (5H, s, ArH), 5.05 (2H, s, OCH2Ph), 4.27 (1H, br s, H-2),
3.70 (3H, s, OCH3) and 3.52 (1H, br s, H-3R); dC (75.5 MHz,
C2HCl3) 173.8 (ester), 157.2 (urethane), 136.7–128.5 (Ar), 70.4
(C-2), 67.3 (OCH2Ph), 53.1 (OCH3) and 44.3 (t, JC,D 21, C-3).
Mosher’s ester (18b) of methyl (2R,3S)-[3-2H1]-N-
benzyloxycarbonylisoserinate
Methyl (2S,3R)-[3-2H1]-N-benzyloxycarbonylisoserinate (17b)
This was prepared by the method described above using
freshly prepared impure methyl (E)-[3-2H1]-acrylate 12b (4.62 g,
53 mmol) and (DHQD)2PHAL (2.07 g, 2.7 mmol) as the
This was prepared by the method described above using methyl
(2R,3S)-[3-2H1]-N-benzyloxycarbonylisoserinate 16b (50 mg,
0.2 mmol). The product 18b (72 mg, 77%) was obtained as a
3 3 5 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6

View Online
Methyl (2R,3R)-[3-2H1]-isoserinate hydrochloride (9a)
32
clear oil; [a]D +34.41 (c 1, CHCl3); m/z [ES+] Found 493.1351,
[C22H21NO7F3 H + Na]+ requires 493.1303; mmax (film)/cm−1
2
A mixture of methyl (2R,3R)-[3-2H1]-N-benzyloxycarbonyl
isoserinate 16a (9 g, 35 mmol), 10% palladium on activated
charcoal (3.75 g) and 32% aqueous hydrochloric acid (1.41 g)
in methanol (100 ml) was stirred vigorously under hydrogen
at room temperature and pressure for 48 h. The solution was
3352 (OH), 1754 (ester) and 1725 (ester); dH (300 MHz, C2HCl3)
7.79 (2H, d, J 8, ArH), 7.17–7.01 (8H, m, ArH), 5.13 (1H,
d, J2,3 6.4, H-2), 4.93 (2H, 2 × d, JA,B 12.4, OCH2Ph), 3.61
(3H, d, JH,F 0.9, OCH3), 4.36 (1H, d, J 6.7, NH), 3.22 (3H, s,
CO2CH3) and 3.15 (2H, d, J3R,2 6.4, H-3R), a signal was present
at 3.39 for OCH3 of the (2S)-isomer; dC (75.5 MHz, C2HCl3)
167.8 (ester), 166.3 (ester), 156.0 (urethane), 129.9–127.8 (Ar),
85.1 (q, JC,F 27.7, CF3), 72.9 (C-2), 66.9 (OCH2Ph), 55.8
(OCH3), 52.3 (OCH3) and 41.2 (t, JC,D 22, C-3); dF (376.4 MHz,
C2HCl3) −72.2 [0.26F, s, (2S)-isomers] and −71.7 [2.74F, s, (2R)-
isomers].
R
filtered through a pad of Celiteꢀ and washed with methanol
(100 ml). The solvent was removed under reduced pressure to
give a yellow oil. Trituration with diethyl ether yielded methyl
(2R,3R)-[3-2H1]-isoserinate hydrochloride 9a (5.54 g, quant.) as
◦
◦
a white solid; mp 99–101 C [lit3 104–105 C]; [a]D +12.88 (c 1,
29
H2O) [lit3 [a]D +18.9 (c 1, H2O)]; m/z [ES+] Found 241.1372,
23
[2 × C4H8NO3 H + H]+ requires 241.1368; m/z [EI+] 121 [M +
2
H, free amine]+; mmax (film)/cm−1 3200 (br, NH3 + OH) and 1732
+
2
(ester); dH (300 MHz, H2O) 4.53 (1H, br s, H-2), 3.75 (3H, s,
Mosher’s ester (19) of methyl (2S)-N-
benzyloxycarbonylisoserinate
2
OCH3) and 3.38 (1H, br s, H-3S); dC (75.5 MHz, H2O) 173.0
(ester), 67.1 (C-2), 53.4 (OCH3) and 41.5 (t, JC,D 23, C-3).
This was prepared by the method described above using methyl
Methyl (2R,3S)-[3-2H1]-isoserinate hydrochloride (9b)
(2S)-N-benzyloxycarbonylisoserinate 17 (50 mg, 0.2 mmol). The
25
product 19 (88 mg, 94%) was obtained as a clear oil; [a]D +8.13
(c 1, CHCl3); m/z [ES+] Found 492.1217, [C22H22NO7F3 + Na]+
requires 492.1240; mmax (film)/cm−1 3345 (OH), 1755 (ester) and
1732 (ester); dH (300 MHz, C2HCl3) 7.79 (2H, d, J 8, ArH),
7.17–7.02 (8H, m, ArH), 5.12 (1H, m, H-2), 4.97 and 4.93 (2H,
AB, JAB 12.2, OCH2Ph), 4.50 (1H, br t, NH), 3.60 (0.3H, s,
other isomer OCH3), 3.39 (3H, d, JH,F 1.1, OCH3), 3.29 (2H,
m, H-3) and 3.19 (3H, s, OCH3); dC (75.5 MHz, C2HCl3) 167.6
(ester), 166.1 (ester), 156.1 (urethane), 129.8–127.9 (Ar), 85.3 (q,
JC,F 28.2, CF3), 72.9 (C-2), 66.9 (OCH2Ph), 55.5 (OCH3), 52.1
(OCH3) and 41.4 (C-3); dF (376.4 MHz, C2HCl3) −72.2 [2.79F, s,
(2S)-isomer] and −71.7 [0.21F, s, (2R)-isomer].
This was prepared by the method described above using methyl
(2R,3S)-[3-2H1]-N-benzyloxycarbonylisoserinate 16b (7.3 g,
28.7 mmol). The product, methyl (2R,3S)-[3-2H1]-isoserinate
hydrochloride 9b (◦4.49 g, quant.) was obtained as a white
solid; mp 99–102 C (lit3 104–105 ◦C); [a]D +12.08 (c 1,
29
H2O) [lit3 +18.6 (c 1, H2O)]; m/z [ES+] Found 241.1366, [2 ×
C4H8NO3 H + H]+ requires 241.1368; m/z [EI+] 121 [M + H,
2
free amine]+; mmax (film)/cm−1 3200 (br, NH3 + OH) and 1733
+
2
(ester); dH (300 MHz, H2O) 4.54 (1H, d, J2,3R 8.3, H-2), 3.76
(3H, s, OCH3) and 3.17 (1H, d, J3R,2 8.3, H-3R); dC (75.5 MHz,
2H2O) 173.0 (ester), 67.2 (H-2), 53.5 (OCH3) and 41.5 (t, JC,D 22,
C-3).
Mosher’s ester (19a) of methyl (2S,3S)-[3-2H1]-N-
benzyloxycarbonylisoserinate
Methyl (2S,3S)-[3-2H1]-isoserinate hydrochloride (11a)
This was prepared by the method described above using methyl
(2S,3S)-N-benzyloxycarbonylisoserinate 17a (14.0 g, 55 mmol).
The product, methyl (2S,3S)-[3-2H1]-isoserinate hydrochloride
11a (8.63 g, quant) was obtained as a white solid; mp 98–100 ◦C
This was prepared by the method described above using methyl
(2S,3S)-[3-2H1]-N-benzyloxycarbonylisoserinate 17a (50 mg,
0.2 mmol). The product 19a (76 mg, 80%) was obtained as a
32
(lit2 102–104 ◦C); [a]D −15.54 (c 1, H2O) [lit2 [a]D −16.6
29
22
clear oil; [a]D +13.32 (c 1, CHCl3); m/z [ES+] Found 493.1289,
2
[C22H21NO7F3 H + Na]+ requires 493.1303; mmax (film)/cm−1
2
(c 1, H2O)]; m/z [ES+] Found 241.1370, [2 × C4H8NO3 H +
3346 (OH), 1754 (ester) and 1727 (ester); dH (300 MHz, C2HCl3)
7.79 (2H, d, J 8, Ar), 7.16–7.02 (8H, m, ArH), 5.12 (1H, d,
J2,3S 4.2, H-2), 4.96 and 4.92 (2H, AB, JAB 12.3, OCH2Ph), 4.5
(1H, d, J 5.6, NH), 3.39 (3H, d, JH,F 1.0, OCH3), 3.29 (1H,
br s, H-3R) and 3.20 (3H, s, OCH3), a signal was present at
3.60 for OCH3 of the (2R)-isomer; dC (75.5 MHz, C2HCl3) 167.6
(ester), 166.3 (ester), 156.1 (urethane), 129.9–127.4 (Ar), 85.3 (q,
JC,F 27.3, CF3), 72.9 (C-2), 66.9 (OCH2Ph), 55.5 (OCH3), 52.2
(OCH3) and 41.2 (t, JC,D 21, C-3); dF (376.4 MHz, C2HCl3) −72.2
[2.75F, s, (2S)-isomers] and −71.7 [0.25F, s, (2R)-isomers].
H]+ requires 241.1368; m/z [EI+] 121 [M + H, free amine]+;
mmax (film)/cm−1 3015 (OH + NH3 ) and 1716 (br, ester); dH
+
(300 MHz, 2H2O) 4.55 (1H, d, J2,3R 3.8, H-2), 3.76 (3H, s, OCH3)
and 3.39 (1H, br s, H-3R); dC (75.5 MHz, H2O) 173.0 (ester),
67.2 (C-2), 53.4 (OCH3) and 41.5 (t, JC,D 22, C-3).
Methyl (2S,3R)-[3-2H1]-isoserinate hydrochloride (11b)
This was prepared by the method described above using methyl
(2S,3R)-[3-2H1]-N-bezyloxycarbonylisoserinate 17b (15.81 g,
60 mmol). The product, methyl (2S,3R)-[3-2H1]-isoserinate
hydrochloride 11b◦ (9.74 g, quant.) was obtained as a white
◦
solid; mp 100–104 C (lit2 101–103 C); [a]D −15.68 (c 1, H2O)
26
Mosher’s ester (19b) of methyl (2S,3R)-[3-2H1]-N-
benzyloxycarbonylisoserinate
21
[lit2 [a]D −18.2 (c 1, H2O)]; m/z [ES+] Found 241.1366, [2 ×
C4H8NO3 H + H]+ requires 241.1368; m/z [EI+] 121 [M + H,
2
This was prepared by the method described above using (2S,3R)-
[3-2H1]-N-benzyloxycarbonylisoserinate 17b (50 mg, 0.2 mmol).
The product 19b (80 mg, 85%) was obtained as a clear
+
free amine]+; mmax (film)/cm−1 2960 (br, OH + NH3 ) and 1733
2
(ester); dH (300 MHz, H2O) 4.55 (1H, d, J2,3S 8.4, H-2), 3.76
(3H, s, OCH3) and 3.18 (1H, d, J3S,2 8.4, H-3S); dC (75.5 MHz,
2H2O) 173.0 (ester), 67.2 (C-2), 53.4 (OCH3) and 41.5 (t, JC,D 22,
C-3).
32
oil; [a]D +14.55 (c 1, CHCl3); m/z [ES+] Found 493.1298,
[C22H21NO7F3 H + Na]+ requires 493.1303; mmax (film)/cm−1
2
3351 (OH), 1753 (ester) and 1725 (ester); dH (300 MHz, C2HCl3)
7.79 (2H, d, J 8, Ar), 7.16–7.03 (8H, m, ArH), 5.13 (1H, d,
J2,3S 6.5, H-2), 4.97 and 4.93 (2H, AB, JAB 13.8, OCH2Ph), 4.57
(1H, d, J 6.5, NH), 3.39 (3H, d, JH,F 1.0, OCH3), 3.28 (1H, d,
J3S,2 6.5, H-3S) and 3.20 (3H, s, OCH3), a signal was present at
3.60 for OCH3 of the (2R)-isomer; dC (75.5 MHz, C2HCl3) 167.6
(ester), 166.1 (ester), 156.1 (urethane), 128.6–127.4 (Ar), 85.3 (q,
JC,F 27.8, CF3), 72.9 (C-2), 66.9 (OCH2Ph), 55.5 (OCH3), 52.1
(OCH3) and 41.2 (t, JC,D 21, C-3); dF (376.4 MHz, C2HCl3) −72.2
[2.275F, s, (2S)-isomers] and −71.7 [0.025F, s, (2R)-isomers].
Methyl (2R,3R)-[3-2H1]-N-triphenylmethylisoserinate (23a)
Methyl (2R,3R)-[3-2H1]-isoserinate hydrochloride 11a (3.6 g,
23 mmol) was suspended in chloroform (50 ml) at room
temperature. Freshly distilled triethylamine (5.12 g, 51 mmol)
was added, and the mixture was stirred for 15 min. The reaction
was cooled to 0 ◦C, triphenylmethyl chloride (6.48 g, 24 mmol)
was added in three portions over a period of 30 min, and the
mixture was stirred at 0 ◦C for 4 h. The reaction was allowed to
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6
3 3 5 3

View Online
warm to room temperature and stirred for a further 18 h. The
mixture was washed with 10% aqueous citric acid (3 × 25 ml)
and water (3 × 25 ml). The organic phase was dried (Na2SO4),
filtered and the solvent was removed under reduced pressure.
The resulting clear oil was purified by flash chromatography on
silica gel using petroleum ether–ethyl acetate (6 : 1) as eluent.
The solvent was removed from the fractions determined to
be homogeneous by TLC to give methyl (2R,3R)-[3-2H1]-N-
triphenylmethylisoserinate 23a (5.43 g, 65%) as a white solid; mp
room temperature for 5 min. Methanesulfonyl chloride (1.48 g,
12.9 mmol) was added dropwise over 15 min and the reaction
was stirred at room temperature for 30 min. The reaction was
heated at reflux for 48 h, allowed to cooled to room temperature,
and the solvent was removed under reduced pressure to give an
orange gum. Ethyl acetate (50 ml) was added, and the solution
was washed with 10% aqueous citric acid (3 × 25 ml) and
saturated aqueous sodium hydrogen carbonate (3 × 25 ml).
The organic phase was dried (MgSO4) and the solvent was
removed under reduced pressure to give the crude product
as orange gum. The orange gum was dissolved in a small
amount of methanol and left standing overnight to give methyl
(2R,3S)-[3-2H1]-N-triphenylmethylaziridine-2-carboxylate 10a
◦
◦
77–81 C [lit3 94–96 C, (2S)-isomer]; [a]D −16.09 (c 1, CHCl3)
36
[lit3 [a]D −16.9 (c 1, CHCl3) of (2S)-isomer]; m/z [ES+] Found
25
2
385.16456, [C23H22NO3 H + Na]+ requires 385.1633; m/z [EI]
361 [M-H]+; mmax (film)/cm−1 3467 (OH) and 1736 (ester); dH
(300 MHz, C2HCl3) 7.45–7.15 (15H, m, ArH), 4.28 (1H, d, J2,3S
3.2, H-2), 3.85 (3H, s, OCH3) and 2.46 (1H, d, J3S,2 3.2, H-3S); dC
(75.5 MHz, C2HCl3) 175.1 (ester), 146.0 (ipso Ar), 129.0–126.8
(Ar), 70.8 (C-2), 70.6 (NCPh3), 53.0 (OCH3), and 46.3 (t, JC,D
21, C-3).
(2.6 g, 89%) as white crystals; mp 126–129 ◦C; [a]D +81.69
24
(c 0.7, MeOH) [lit2 [a]D +103.0 (c 0.7, MeOH)]; m/z [ES+]
23
Found 367.1538, [C23H20NO2 H + Na]+ requires 367.1527;
2
mmax (film)/cm−1 1748 (ester); dH (300 MHz, C2HCl3) 7.51–7.19
(15H, m, ArH), 3.76 (3H, s, OCH3), 2.25 (1H, d, J3R,2 2.7,
H-3R) and 1.88 (1H, d, J2,3R 2.7, H-2); dC (75.5 MHz, C2HCl3)
172.4 (ester), 144.0 (ipso Ar), 129.7–127.4 (m, p, o Ar), 74.8
(NCPh3), 52.6 (OCH3), 32.0 (C-2) and 28.9 (t, JC,D 25. C-3).
Methyl (2R,3S)-[3-2H1]-N-triphenylmethylisoserinate (23b)
This was prepared by the method described above
using methyl (2R,3S)-[3-2H1]-isoserinate hydrochloride 9b
(5.51 g, 35.2 mmol). The product methyl (2R,3S)-[3-2H1]-N-
triphenylmethylisoserinate 23b (6.9 g, 57%) was obtained as a
Methyl (2R,3R)-[3-2H1]-N-triphenylmethylaziridine-2-
carboxylate (10b)
white solid; mp 80–82 ◦C; [a]D −15.42 (c 1, CHCl3); m/z [ES+]
34
Found 385.1626, [C23H22NO3 H + Na]+ requires 385.1633; m/z
2
This was prepared by the method above using methyl (2S,3R)-[3-
2H1]-N-triphenylmethylisoserinate 20b (9.80 g, 27.1 mmol). The
product methyl (2R,3R)-[3-2H1]-N-triphenylmethylaziridine-2-
carboxylate 10b (5.68 g, 60%) was obtained as white crystals; mp
[EI+] 361 [M–H]+; mmax (film)/cm−1 3466 (OH) and 1734 (ester);
dH (300 MHz, C2HCl3) 7.46–7.03 (15H, m, ArH), 4.29 (1H, d,
J2,3R 4.5, H-2), 3.86 (3H, s, OCH3) and 2.51 (1H, d, J3R,2 4.5,
H-3R); dC (75.5 MHz, C2HCl3) 175.1 (ester), 146.0 (ipso Ar),
129.0–126.8 (Ar), 70.8 (C-2), 70.6 (NCPh3), 53.0 (OCH3) and
46.4 (t, JC,D 21, C-3).
124–126 ◦C; [a]D +66.64 (c 0.7, MeOH) [lit2 [a]D +101.6 (c 0.7,
27
23
MeOH)]; m/z [ES+] Found 367.1522, [C23H20NO2 H + Na]+
2
requires 367.1527; mmax (film)/cm−1 1749 (ester); dH (300 MHz,
C2HCl3) 7.51–7.20 (15H, m, ArH), 3.77 (3H, s, OCH3), 1.88 (1H,
d, J2,3S 6.2, H-2) and 1.41 (1H, d, J3S,2 6.2, H-3S); dC (75.5 MHz,
C2HCl3) 172.4 (ester), 144.0 (ipso Ar), 129.7–127.3 (Ar), 74.8
(NCPh3), 52.5 (OCH3), 32.0 (C-2) and 28.8 (t, JC,D 26. C-3).
Methyl (2S,3S)-[3-2H1]-N-triphenylmethylisoserinate (20a)
This was prepared by the method described above us-
ing methyl (2S,3S)-[3-2H1]-isoserinate hydrochloride 11a
(3.10 g, 20 mmol). The product methyl (2S,3S)-[3-2H1]-N-
triphenylmethylisoserinate◦20a (4.40 g, 61%) was obtained as
Methyl (2S,3R)-[3-2H1]-N-triphenylmethylaziridine-2-
carboxylate (8a)
a white solid; mp 78–83 C [lit2 82–84 ◦C); [a]D +16.42 (c
33
1, CHCl3) [lit2 [a]D +15.2 (c 1, CHCl3)]; m/z [ES+] Found
24
385.1628, [C23H22NO3 H + Na]+ requires 385.1633; m/z [EI]
2
This was prepared by the method described above us-
ing methyl (2R,3R)-[3-2H1]-N-triphenylmethylisoserinate 23a
(4.7 g, 13 mmol). The product methyl (2S,3S)-[3-2H1]-N-
triphenylmethylaziridine-2-carboxylate 8a (3.38 g, 76%) was
361 [M–H]+; mmax (film)/cm−1 3481 (OH) and 1737 (ester); dH
(300 MHz, C2HCl3) 7.45–6.90 (15H, m, ArH), 4.28 (1H, d, J2,3R
3.5, H-2), 3.84 (3H, s, OCH3) and 2.46 (1H, d, J3R,2 3.5, H-3R); dC
(75.5 MHz, C2HCl3) 175.1 (ester), 146.1 (ipso Ar), 129.0–126.8
(Ar), 70.8 (H-2), 70.7 (NCPh3), 53.0 (OCH3), 46.4 (t, JC,D 21,
C-3).
◦
obtained as white crystals; mp 123–125 C (lit3 126–128 ◦C);
[a]D −99.40 (c 0.7, MeOH) [lit3 [a]D −86.8 (c 0.7, CHCl3)];
27
25
m/z [ES+] Found 367.1526, [C23H20NO2 H + Na]+ requires
2
367.1527; mmax (film)/cm−1 1748 (ester); dH (300 MHz, C2HCl3)
7.52–7.20 (15H, m, ArH), 3.77 (3H, s, OCH3), 2.25 (1H, d,
J3S,2 2.6, H-3S) and 1.88 (1H, d, J2,3S 2.6, H-2); dC (75.5 MHz,
C2HCl3) 172.4 (ester), 144.0 (ipso Ar), 129.7–127.3 (Ar), 74.8
(NCPh3), 52.5 (OCH3), 32.0 (C-2) and 28.8 (t, JC,D 26. C-3).
Methyl (2S,3R)-[3-2H1]-N-triphenylmethylisoserinate (20b)
This was prepared by the method described above us-
ing methyl (2S,3R)-[3-2H1]-isoserinate hydrochloride 11b
(4.97 g, 32 mmol). The product methyl (2S,3R)-[3-2H]-N-
triphenylmethylisoserinate 20b (8.30 g, 72%) was obtained
as a white solid; mp 80–84 ◦C; [a]D +15.24 (c 1, CHCl3)
33
24
[lit2 [a]D +15.6 (c 1, CHCl3)]; m/z [ES+] Found 385.1651,
Methyl (2S,3S)-[3-2H1]-N-triphenylmethylaziridine-2-
carboxylate (8b)
[C23H22NO3 H + Na]+ requires 385.1633; m/z [EI] 361 [M–H]+;
2
mmax (film)/cm−1 3468 (OH) and 1736 (ester); dH (300 MHz,
C2HCl3) 7.45–6.92 (15H, m, ArH), 4.29 (1H, d, J2,3S 4.7, H-
2), 3.87 (3H, s, OCH3) and 2.51 (1H, d, J3S,2 4.7, H-3S); dC
(75.5 MHz, C2HCl3) 175.1 (ester), 146.0 (ipso Ar), 129.0–126.8
(Ar), 70.8 (C-2), 70.7 (NCPh3), 53.0 (OCH3) and 46.4 (t, JC,D 22,
C-3).
This was prepared by the method described above us-
ing methyl (2R,3S)-[3-2H1]-N-triphenylmethylisoserinate 23b
(5.8 g, 16 mmol). The product methyl (2S,3S)-[3-2H1]-N-
triphenylmethylaziridine-2-carboxylate 8b (3.36 g, 61%)◦ was
obtained as white crystals; mp 125–128 ◦C (lit3 mp 127–129 C));
[a]D −73.97 (c 0.7, MeOH) (lit3 [a]D −86.3 (c 1, CHCl3);
27
25
m/z [ES+] Found 367.1532, [C23H20NO2 H + Na]+ requires
2
Methyl (2R,3S)-[3-2H1]-N-triphenylmethylaziridine-2-
carboxylate (10a)
367.1527; mmax (film)/cm−1 1747 (ester); dH (300 MHz, C2HCl3)
7.51–7.20 (15H, m, ArH), 3.76 (3H, s, OCH3), 1.88 (1H, d,
J2,3R 6.2, H-2) and 1.41 (1H, d, J3R,2 6.2, H-3R); dC (75.5 MHz,
C2HCl3) 172.4 (ester), 144.0 (ipso Ar), 129.7–127.3 (m, p, o Ar),
74.8 (NCPh3), 52.5 (OCH3), 32.0 (C-2) and 28.8 (t, JC,D 27, C-3).
Methyl
(2S,3S)-[3-2H1]-N-triphenylmethylisoserinate
20a
(3.10 g, 8.56 mmol) was dissolved in THF (45 ml), triethylamine
(3.08 g, 30 mmol) was added and the mixture was stirred at
3 3 5 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6

View Online
Methyl (2R,3S)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
carboxylate (21a)
53.1 ◦C; [a]D −27.9 (c 1.5, CHCl3) [lit2 [a]D −35.5 (c 1.5,
30
30
CHCl3)]; m/z [ES+] Found 295.0579, [C12H13NO4 HCl + Na]+
2
requires 295.0566; mmax (film)/cm−1 3337 (NH) and 1720 (br,
ester and urethane); dH (300 MHz, C2HCl3) 7.34 (5H, br s,
ArH), 5.76 (1H, br, NH), 5.13 (2H, s, OCH2Ph), 4.77 (1H,
m, H-2), 3.96 (0.1H, br s, unlabelled), 3.86 (0.9H, d, J3S,2 3.3,
H-3S) and 3.81 (3H, s, OCH3); dC (75.5 MHz, C2HCl3) 169.6
(ester), 156.0 (urethane), 136.3 (ipso Ar), 129.0–128.5 (Ar), 67.7
(OCH2Ph), 55.1 (C-2), 53.4 (OCH3) and 45.4 (t, JC,D 23, C-3).
This was prepared by the method reported in ref. 2 using methyl
(2R,3S)-[3-2H1]-N-triphenylmethylaziridine-2-carboxylate 10a
(500 mg, 1.45 mmol) to yield methyl (2R,3S)-[3-2H1]-N-
benzyloxycarbonylaziridine-2-carboxylate 21a (295 mg, 86%)
as a clear oil; [a]D +53.3 (c 0.7, CHCl3) [lit2 [a]D +42.5 (c
25
23
2
0.7, CHCl3)]; m/z (ES+) Found 259.0819, [C12H12NO4 H +
Na]+ requires 259.07996; mmax (film)/cm−1 1732 (br, ester and
urethane); dH (300 MHz, C2HCl3) 7.45–7.29 (5H, br s, ArH),
5.15 (2H, s, OCH2Ph), 3.71 (3H, s, OCH3), 3.11 (1H, d, J2,3R 3.2,
H-2) and 2.59 (1H, d, J3R,2 3.2, H-3R); dC (75.5 MHz, C2HCl3)
168.6 (ester), 160.7 (urethane), 135.3 (ipso Ar), 128.6–128.1 (Ar),
68.6 (OCH2Ph), 52.7 (OCH3), 34.8 (C-2) and 31.1 (t, JC,D 27,
C-3).
Methyl (2S,3S)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
This was prepared as above using methyl (2R,3R)-[3-2H1]-N-benz-
yloxycarbonylaziridine-2-carboxylate 24b (500 mg, 2.13 mmol)
to yield methyl (2S,3S)-[3-2H1]-N-benzyloxycarbonyl-b-
chloroalaninate (267 mg, 46%) as a white solid; mp 51.9–54.2 ◦C;
[a]D −29.21 (c 1.5, CHCl3) [lit2 [a]D −35.9 (c 1.03, CHCl3)];
30
22
Methyl (2R,3R)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
carboxylate (21b)
m/z [ES+] Found 295.0562, [C12H13NO4 HCl + Na]+ requires
2
295.0566; mmax (film)/cm−1 3337 (NH) and 1723 (br, ester and
urethane); dH (300 MHz, C2HCl3) 7.37 (5H, br s, ArH), 5.70
(1H, br, NH), 5.14 (2H, s, OCH2Ph), 4.77 (1H, m, H-2), 3.99
(0.92H, d, J3R,2 2.9, H-3R), 3.86 (0.08H, br s, unlabelled) and
3.81 (3H, s, OCH3); dC (75.5 MHz, C2HCl3) 169.6 (ester), 156.0
(urethane), 136.3 (ipso Ar), 129.0–128.5 (Ar), 67.7 (OCH2Ph),
55.1 (C-2), 53.5 (OCH3) and 45.4 (t, JC,D 24, C-3).
This was prepared as above using methyl (2R,3R)-[3-2H1]-N-
triphenylmethylaziridine-2-carboxylate 10b (1 g, 2.9 mmol) to
yield methyl (2R,3R)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
35
carboxylate 21b (669 mg, 98%) as a clear oil; [a]D +59.8
24
(c 0.7, CHCl3) [lit2 [a]D +40.6 (c 0.7, CHCl3)]; m/z (ES+)
Found 259.0824, [C12H12NO4 H + Na]+ requires 259.07996; mmax
2
(film)/cm−1 1745 (br, ester and urethane); dH (300 MHz, C2HCl3)
7.36 (5H, br s, ArH), 5.15 (2H, s, OCH2Ph), 3.72 (3H, s, OCH3),
3.11 (1H, d, J2,3S 5.4, H-2) and 2.48 (1H, d, J3S,2 5.4, H-3S); dC
(75.5 MHz, C2HCl3) 169.0 (ester), 161.1 (urethane), 135.7 (ipso
Ar), 129.0–128.9 (Ar), 69.0 (OCH2Ph), 53.0 (OCH3), 35.2 (C-2)
and 31.5 (t, JC,D 27, C-3).
Methyl (2R,3S)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
This was prepared by the method described above us-
ing methyl (2S,3R)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
carboxylate 24a (200 mg, 0.85 mmol). Methyl (2R,3S)-[3-2H1]-
N-benzyloxycarbonyl-b-chloroalaninate (186 mg, 80%) was
Methyl (2S,3R)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
carboxylate (24a)
obtained as a white solid; mp 52.5–55.7 ◦C; [a]D +13.9 (c 1.5,
32
CHCl3); m/z [ES+] Found 295.0577, [C12H13NO4 HCl + Na]+
2
requires 295.0566; mmax (thin film)/cm−1 3337 (NH) and 1721
(br, ester and urethane); dH (300 MHz, C2HCl3) 7.34 (5H, br s,
ArH), 5.75 (1H, br, NH), 5.13 (2H, s, OCH2Ph), 4.77 (1H, m,
H-2), 3.96 (0.06H, br s, unlabelled), 3.86 (0.94H, d, J3R,2 3.2,
H-3R) and 3.81 (3H, s, OCH3); dC (75.5 MHz, C2HCl3) 169.6
(ester), 156.0 (urethane), 136.3 (ipso Ar), 129.0–128.5 (Ar), 67.7
(OCH2Ph), 55.1 (C-2), 53.4 (OCH3) and 45.4 (t, JC,D 23, C-3).
This was prepared by the method described above using methyl
(2S,3R)-[3-2H1]-N-triphenylmethylaziridine-2-carboxylate 8a
(500 mg, 1.45 mmol). The product methyl (2S,3R)-[3-2H1]-
N-benzyloxycarbonylaziridine-2-carboxylate 24a (325 mg,
36
95%) was obtained as a clear oil; [a]D −21.0 (c 0.7, CHCl3);
m/z (ES+) Found 259.0814, [C12H12NO4 H + Na]+ requires
2
259.07996; mmax (thin film)/cm−1 1736 (br, ester and urethane);
dH (300 MHz, C2HCl3) 7.36 (5H, br s, ArH), 5.15 (2H, s,
OCH2Ph), 3.72 (3H, s, OCH3), 3.11 (1H, d, J2,3S 3.2, H-2) and
2.60 (1H, d, J3S,2 3.2, H-3S); dC (75.5 MHz, C2HCl3) 168.6
(ester), 160.7 (urethane), 135.3 (ipso Ar), 128.6–127.0 (Ar), 68.6
(OCH2Ph), 52.7 (OCH3), 34.7 (C-2) and 31.1 (t, JC,D 27, C-3).
Methyl (2R,3R)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
This was prepared by the method described above us-
ing methyl (2S,3S)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
carboxylate 24b (200 mg, 0.85 mmol). Methyl (2R,3R)-[3-2H1]-
N-benzyloxycarbonyl-b-chloroalaninate (199 mg, 86%) was
Methyl (2S,3S)-[3-2H1]-N-benzyloxycarbonylaziridine-2-
carboxylate (24b)
obtained as a white solid; mp 50.9–53.4 ◦C; [a]D +37.07 (c 1.5,
32
CHCl3); m/z [ES+] Found 295.0573, [C12H13NO4 HCl + Na]+
2
This was prepared by the method described above using methyl
(2S,3S)-[3-2H1]-N-triphenylmethylaziridine-2-carboxylate 8b
(500 mg, 1.45 mmol). The product methyl (2S,3S)-[3-2H1]-
N-benzyloxycarbonylaziridine-2-carboxylate 24b (313 mg,
requires 295.0566; mmax (thin film)/cm−1 3338 (NH) and 1720
(br, ester and urethane); dH (300 MHz, C2HCl3) 7.34 (5H, br s,
ArH), 5.70 (1H, br, NH), 5.13 (2H, s, OCH2Ph), 4.77 (1H, m,
H-2), 3.96 (0.93H, br s, H-3S), 3.88 (0.07H, br s, unlabelled) and
3.80 (3H, s, OCH3); dC (75.5 MHz, C2HCl3) 169.6 (ester), 156.0
(urethane), 136.3 (ipso Ar), 129.0–128.5 (Ar), 67.7 (OCH2Ph),
55.1 (C-2), 53.4 (OCH3) and 45.4 (t, JC,D 24, C-3).
36
92%) was obtained as a clear oil; [a]D −45.6 (c 0.7, CHCl3);
2
m/z (ES+) Found 259.0810, [C12H12NO4 H + Na]+ requires
259.07996; mmax (thin film)/cm−1 1744 (br, ester and urethane);
dH (300 MHz, C2HCl3) 7.36 (5H, br s, ArH), 5.15 (2H, s,
OCH2Ph), 3.72 (3H, s, OCH3), 3.11 (1H, d, J2,3R 5.4, H-2) and
2.48 (1H, d, J3R,2 5.4, H-3R); dC (75.5 MHz, C2HCl3) 168.6
(ester), 160.7 (urethane), 135.3 (ipso Ar), 128.6–127.0 (Ar),
68.6 (OCH2Ph), 52.7 (OCH3), 34.8 (C-2) and 31.5 (t, JC,D 27,
C-3).
(2S,3R)-[3-2H1]-b-Chloroalanine (22a)
This was prepared by the method reported in ref. 2 from methyl
(2S,3R)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate 21a
(70 mg, 0.26 mmol) to yield (2S,3R)-[3-2H1]-b-chloroalanine
Methyl (2S,3R)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
37
22a (18 mg, 55%) as a cream solid; decomp on mp; [a]D +4.92
26
This was prepared as above using methyl (2R,3S)-[3-2H1]-N-benz-
yloxycarbonylaziridine-2-carboxylate 24a (200 mg, 0.85 mmol)
to yield methyl (2S,3R)-[3-2H1]-N-benzyloxycarbonyl-b-
chloroalaninate (174 mg, 76%) as a white solid; mp 52.0–
(c 0.5, H2O) [lit2 [a]D +7.1 (c 0.57, H2O)]; dH (300 MHz, 10%
2HCl in 2H2O, Fig. 3c) 4.50 (1H, br s, H-2) and 3.93 (1H, br s,
2
2
H-3S); dC (75.5 MHz, 10% HCl in H2O) 167.6 (acid), 53.0
(C-2) and 40.8 (t, JC,D 22, C-3).
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6
3 3 5 5

View Online
(2S,3S)-[3-2H1]-b-Chloroalanine (22a)
Acknowledgements
This was prepared as for the (2R)-isomer above from
methyl (2S,3S)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
(70 mg, 0.26 mmol) to yield (2S,3S)-[3-2H1]-b-chloroalanine 22a
as a cream solid; decomp on mp; [a]D37.5 +3.76 (c 0.5, H2O); dH
We thank the EPSRC for financial assistance, Dr A. G. Avent
for some NMR spectra and Dr A. Al Sada for high resolution
mass spectra.
2
2
(300 MHz, 10% HCl in H2O, Fig. 3b) 4.50 (1H, d, J2,3R 4.0,
H-2) and 3.90 (1H, d, J3R,2 4.0, H-3R); dC (75.5 MHz, 10% 2HCl
in 2H2O) 167.6 (acid), 53.0 (C-3) and 41.0 (t, JC,D 23, C-3).
References
1 D. W. Young, Top. Stereochem., 1994, 21, 381–465.
2 B. S. Axelsson, K. J. O’Toole, P. A. Spencer and D. W. Young, J. Chem.
Soc., Perkin Trans. 1, 1994, 807–816.
3 K. J. M. Beresford and D. W. Young, Tetrahedron, 1996, 52, 9891–
9900.
4 N. J. Church and D. W. Young, J. Chem. Soc., Perkin Trans. 1, 1998,
1475–1482.
5 B. S. Axelsson, H. G. Floss, S. Lee, A. Saeed, P. A. Spencer and D. W.
Young, J. Chem. Soc., Perkin Trans. 1, 1994, 2137–2142.
6 B. S. Axelsson, N. J. Church, P. A. Spencer and D. W. Young, Folia
Microbiol., 1995, 40, 17–22.
(2R,3S)-[3-2H1]-b-Chloroalanine (25a)
This was prepared by the method described above using
methyl (2R,3S)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
(89 mg, 0.33 mmol). The product, (2R,3S)-[3-2H1]-b-
chloroalanine 25a was obtained as a cream solid (25 mg, 64%);
mp decomp; [a]D −6.83 (c 0.5, H2O); dH (300 MHz, 10% 2HCl
34
in 2H2O, Fig. 4b) 4.50 (1H, d, J2,3R 3.0, H-2) and 3.95 (1H, br s,
2
2
H-3R); dC (75.5 MHz, 10% HCl in H2O) 167.6 (acid), 53.0
7 B. Adams, K. J. M. Beresford, S. M. Whyte and D. W. Young, Chem.
Commun., 2000, 619–620.
(C-2) and 41.0 (br m, C-3).
8 B. Adams, B. S. Axelsson, K. J. M. Beresford, N. J. Church, P. A.
Spencer, S. M. Whyte and D. W. Young, Pure Appl. Chem., 2000, 72,
373–384.
9 D. H. G. Crout and J. A. Corkill, Tetrahedron Lett., 1977, 18, 4355–
4357.
(2R,3R)-[3-2H1]-b-Chloroalanine (25b)
This was prepared by the method described above using
methyl (2R,3R)-[3-2H1]-N-benzyloxycarbonyl-b-chloroalaninate
(100 mg, 0.37 mmol). (2R,3R)-[3-2H1]-b-Chloroalanine (142)
10 G. Just and R. Ouellet, Can. J. Chem., 1976, 54, 2925–2934.
11 G. Li, H. H. Angert and K. B. Sharpless, Angew. Chem., Int. Ed.
Engl., 1996, 35, 2813–2817.
30
(26 mg, 57%), was obtained as a cream solid; mp decomp; [a]D
2
2
−7.11 (c 0.5, H2O); dH (300 MHz, 10% HCl in H2O, Fig. 4c)
4.50 (1H, d, J2,3S 4.2, H-2) and 4.04 (1H, d, J3S,2 4.2, H-3S); dC
(75.5 MHz, 10% 2HCl in 2H2O) 167.6 (acid), 53.0 (C-2) and 41.0
(t, JC,D 23, C-3).
12 M. J. Mintz, Organic Synthesis, Coll. Vol. 5, ed H. E. Baumgarten,
Wiley, New York, 1973, pp. 183–187.
13 U. Schmidt, R. Meyer, V. Leitenberger, F. Sta¨bler and A.
Leibenknecht, Synthesis, 1991, 5, 409–414.
3 3 5 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 3 4 8 – 3 3 5 6