Solvent-mediated selective single and double ring-opening of N-tosyl-activated aziridines using benzylamine

Article abstract of DOI:10.1016/S0957-4166(02)00102-7

An efficient methodology has been developed for the synthesis of a series of new diamine 2 and triamine ligands 3 for application in asymmetric catalysis via selective single or double ring-opening of tosylaziridines 1, which are derived from chiral pool

Full text of DOI:10.1016/S0957-4166(02)00102-7

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 13 (2002) 269–272
Solvent-mediated selective single and double ring-opening of
N-tosyl-activated aziridines using benzylamine
J. Erik W. Scheuermann, Gennadiy Ilyashenko, D. Vaughan Griffiths and Michael Watkinson*
Department of Chemistry, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
Received 31 January 2002; accepted 25 February 2002
Abstract—An efficient methodology has been developed for the synthesis of a series of new diamine 2 and triamine ligands 3 for
application in asymmetric catalysis via selective single or double ring-opening of tosylaziridines 1, which are derived from chiral
pool amino acids. The selectivity of the ring-opening reaction is readily controlled by the solvent employed. Thus, in acetonitrile
formation of secondary amines 2 occurs via a single ring-opening step, whilst in methanol the reactions proceed to give the tertiary
amines 3 via the ring-opening of two aziridine molecules. © 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
acyl halide–aldehyde cyclocondensations.4 To maximise
the structural diversity of the ligands available to us, we
were particularly interested in developing highly
chemoselective routes towards both diamine and tri-
amine ligands, such as 2 and 3, via single and double
ring-opening of activated aziridines. Our rationale for
seeking to broaden the scope of the ligands produced
lies in the empirical nature of the discovery process for
asymmetric catalysts and the consequential requirement
for ligand libraries containing as much structural diver-
sity as possible when screening for activity.5
The development and application of new homochiral
ligands in asymmetric catalysis continues to be an area
of enormous interest and activity, since this approach
represents one of the most efficient means of obtaining
enantiopure chiral compounds.1 We are currently inter-
ested in the development of small ligand libraries to
enable us to screen the catalytic activity of their transi-
tion metal complexes in a number of asymmetric trans-
formations using diversity methods. Aziridines are ideal
starting materials for this purpose2 and our interest in
the area has been further stimulated by a number of
reports of the successful application of related C2- and
C3-symmetric ligands, derived from chiral pool amino
acids, in asymmetric catalysis; examples include
diethylzinc additions to benzaldehyde3 and aldol-like
2. Results and discussion
The N-tosyl-aziridines, 1, used in this study were pre-
pared in an identical manner from the appropriate
Scheme 1.
* Corresponding author. Tel.: +44 (0)20 7882 3263; fax: +44 (0)20 7882 7794; e-mail: m.watkinson@qmul.ac.uk
0957-4166/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(02)00102-7

270
J. E. W. Scheuermann et al. / Tetrahedron: Asymmetry 13 (2002) 269–272
amino alcohol using slight modifications of the
reported procedure.6 We then attempted to facilitate
ring opening of these materials at the methylene car-
bon using benzylamine as the amine nucleophile under
a range of classical conditions.2 The choice of benzyl-
amine was based on our recent experience that had
demonstrated it to be an ideal nucleophile and the fact
that the benzyl group could be readily removed in
related polyamine systems.7 Therefore, its presence in
2 and 3 would readily allow for the selective introduc-
tion of further structural modularity in the ligand
library, if needed, through appropriate deprotection/
alkylation strategies.
straightforward through recrystallisation of the crude
reaction mixture.
The simple procedures optimised for 1a were then
applied to four other activated aziridines 1b–e. In all
cases the ring-opening of the aziridines proceeded in
an analogous manner and homogeneous samples of
single and double ring-opened products could be pre-
pared in moderate to good yield (Table 1, entries
3–10). To the best of our knowledge only one of these
compounds, 3c, has been previously applied in asym-
metric catalysis when an aluminium complex was
shown to be a moderately selective catalyst in an
asymmetric acyl halide–aldehyde cyclocondensation,4
although we have been unable to find any experimen-
tal data.
It quickly became apparent from an initial screen of
reaction conditions using 1a, that considerable
chemoselectivity could be achieved in the ring-opening
reaction simply by modifying the reaction solvent
(Scheme 1). Thus, for example, when 1a was reacted
with benzylamine in a 1:1 molar ratio in acetonitrile
the secondary amine 2a was formed almost exclu-
sively, whereas in methanol a mixture of 2a and 3a
resulted. The observed tendency for double ring-open-
ing in methanol could be exploited and by reacting 1a
with benzylamine in a 2:1 ratio, 3a was exclusively
formed. In contrast, using this 2:1 reactant ratio with
acetonitrile as the solvent essentially still resulted in
the formation of only the secondary amine 2a. Only
after heating the reaction mixture under reflux in the
presence of excess 1a for a week was 3a formed. In
this case it remained contaminated with 2a and was
difficult to purify and the reaction was consequently
low yielding. In contrast, 2a could be readily con-
verted to 3a in methanol by the addition of a further
equivalent of 1a at reflux. Optimisation of the results
of this initial screen resulted in the isolation of 2a and
3a in 62 and 69% yield, respectively (Table 1, entries 1
and 2). The double ring-opening of three N-tosyl
aziridines using aqueous ammonia and methylamine
has been reported by Lin and co-workers.8 However,
this is a more complicated procedure that first requires
the single ring-opened product to be prepared, more-
over the products are all isolated by column chro-
matography. In contrast both single, 2a, and double,
3a, ring-opened products could be readily isolated
from the crude reaction mixture without the need for
chromatography; the isolation of 3a being particularly
3. Conclusion
We have discovered that careful choice of the reaction
solvent can provide an extremely simple methodology
for controlling the ring-opening of activated N-tosyl-
aziridines, 1, by benzylamine to generate the new
enantiomerically pure diamine- and triamine-ligands 2
and 3. The use of acetonitrile results in the exclusive
formation of the single ring-opened products 2, whilst
the use of methanol produces the double ring-opened
materials 3. The procedure is particularly convenient,
as both products can be isolated in a pure state fol-
lowing a simple work up procedure.
4. Experimental
4.1. General methods
All reagents were commercially available and were
used without further purification, unless otherwise
stated. CH3CN was heated under reflux overnight with
CaH2 in an atmosphere of nitrogen and then distilled
from CaH2. Methanol was heated under reflux for 3 h
over Mg turnings together with a small quantity of
iodine and then distilled. Benzylamine was dried over
KOH pellets prior to use. Nitrogen for inert atmo-
sphere use was purified by passing it through anhy-
,
drous manganese(II) oxide, 3 A molecular sieves and
highly reduced chromium adsorbed onto a silica sup-
port. Thin-layer chromatography (TLC) was per-
formed on silica gel 60 F254 plates (Merck). Melting
points were determined using an Electrothermal melt-
ing point apparatus and are uncorrected. Elemental
analyses were obtained using a Carlo Erba 1106 ele-
Table 1. Chemoselective ring opening of aziridines 1 with
benzylamine
Entry
Ligand
R
Solvent
Yield (%)
1
mental analyser. H NMR and 13C NMR spectra were
1
2
3
4
5
6
7
8
9
2a
3a
2b
3b
2c
3c
2d
3d
2e
3e
Pri
CH3CN
MeOH
CH3CN
MeOH
CH3CN
MeOH
CH3CN
MeOH
62
69
56
69
49
80
60
44
42
79
recorded as CDCl3 solutions on a JEOL JNM-EX
spectrometer at 270 and at 67.9 MHz, respectively. All
1H NMR spectra were referenced to residual CHCl3 as
the internal standard with J values are given in hertz.
IR spectra were recorded on a Perkin–Elmer 1720X
FT-IR spectrometer with a solid state ATR attach-
ment. Mass spectra were recorded on a VG Instru-
ments ZAB-SE using xenon gas at 8 kV in a matrix of
3-nitrobenzyl alcohol (MNBA) and sodium iodide
(FAB).
Pri
CH3
CH3
Bn
Bn
(CH3)2CHCH2
(CH3)2CHCH2
CH3CH2CH(CH3) CH3CN
CH3CH2CH(CH3) MeOH
10

J. E. W. Scheuermann et al. / Tetrahedron: Asymmetry 13 (2002) 269–272
271
4.2. General procedure for the preparation of the sec-
ondary amines 2 via the ring-opening of N-tosyl-aziridi-
nes 1 with benzylamine
68.5; H, 6.7; N, 6.9. Found: C, 68.6; H, 6.1; N, 6.6.
FABMS (m/z): 395 (100%) [M+H]. HRMS (FAB)
calcd for C23H27N2O2S [M+H] 395.1793; found:
395.1810.
All reactions were carried out in an identical manner to
yield products that were homogeneous by TLC. All
yields are based on the aziridine 1 (Table 1) and the
procedure used is typified by the preparation of 2a. It
was found that the addition of a slight excess of benzyl-
amine resulted in cleaner reactions and easier product
purification.
14.2.4.
N-[1-(Benzylaminomethyl)-3-methylbutyl]-4-
methylbenzenesulfonamide 2d. Colourless waxy-solid.
1
[h]2D5 −19.2 (c 0.5, CHCl3). H NMR: l 7.71 (d, 2H,
J=8.2), 7.32–7.14 (m, 7H), 3.57 (s, 2H), 3.32–3.21 (m,
1H), 2.52–2.40 (m, 2H), 2.36 (s, 3H), 1.52 (nonet, 1H,
J=6.7), 1.38–1.27 (m, 1H), 1.22–1.12 (m, 1H), 0.77 (d,
3H, J=6.7), 0.72 (d, 3H, J=6.7). 13C NMR: l 143.2,
139.9, 138.0, 129.7, 128.5, 128.1, 127.2, 127.1, 53.6,
52.2, 51.7, 43.0, 24.5, 22.7, 22.4, 21.6. IR (wmax/cm−1):
3277, 2955, 1453, 1328, 1160, 1093, 965, 910, 814, 731,
699, 667, 631, 544. Anal. calcd for C20H28N2O2S: C,
66.6; H, 7.8; N, 7.8. Found: C, 66.8; H, 8.2; N, 7.6.
FABMS (m/z): 361 (100%) [M+H]. HRMS (FAB)
calcd for C20H28N2O2S [M+H] 361.1950; found:
361.1958.
4.2.1.
N-[1-(Benzylaminomethyl)-2-methylpropyl]-4-
methylbenzenesulfonamide 2a. N-Tosyl-aziridine, 1a
(2.00 g, 8.37 mmol) and benzylamine (1.00 g, 9.35
mmol) were dissolved in dry acetonitrile (30 mL) and
the mixture stirred under reflux for 3 days. The solvent
was evaporated under reduced pressure and the slightly
yellow residue dissolved in diethyl ether (30 mL). Upon
the addition of concentrated hydrochloric acid (2 mL)
the desired product precipitated as its HCl salt. The
colourless crystals were collected, dissolved in H2O (30
mL), basified to pH 12 with solid KOH and extracted
with dichloromethane (3×50 mL). The combined
organic extracts were then dried with anhydrous mag-
nesium sulfate and the solvent evaporated under
reduced pressure, resulting in a colourless waxy-solid
4.2.5.
N-[1-(Benzylaminomethyl)-2-methylbutyl]-4-
methylbenzenesulfonamide 2e. Colourless waxy-solid.
[h]2D5 −3.6 (c 0.5, CHCl3). 1H NMR: l 7.70 (d, 2H,
J=8.2), 7.31–7.15 (m, 7H), 3.51 (s, 2H), 3.13–3.06 (m,
1H), 2.52 (dd, 1H, J=12.4 and 7.4), 2.39 (dd, 1H,
J=12.4 and 4.2), 2.34 (s, 3H), 1.67–1.52 (m, 1H),
1.46–1.31 (m, 1H), 1.11–0.95 (m, 1H) 0.83–0.75 (m,
6H). 13C NMR: l 143.2, 139.9, 137.7, 129.7, 128.5,
128.1, 127.2, 127.1, 57.2, 53.5, 48.0, 37.2, 25.8, 21.6,
14.4, 11.9. IR (wmax/cm−1): 3534, 3312, 3065, 2963, 2877,
1674, 1597, 1493, 1475, 1453, 1381, 1317, 1302, 1208,
1182, 1157, 1130, 1111, 1090, 1046, 1030, 954, 868, 811,
752, 697, 577, 541 cm−1. FABMS (m/z): 361 (100%)
[M+H]. HRMS (FAB) calcd for C20H28N2O2S [M+H]
361.1950; found: 361.1958.
1
(1.8 g, 5.19 mmol, 62%). [h]2D5 −18.8 (c 0.5, CHCl3). H
NMR: l 7.68 (d, 2H, J=8.4), 7.33–7.16 (m, 7H), 3.54
(s, 2H), 3.03–2.97 (m, 1H), 2.55 (dd, 1H, J=12.4 and
6.8), 2.38 (dd, 1H, J=12.4 and 4.5), 2.36 (s, 3H), 1.83
(octet, 1H, J=6.8), 0.84 (d, 3H, J=6.8), 0.79 (d, 3H,
J=6.8). 13C NMR: l 143.1, 139.8, 137.7, 129.5, 128.4,
127.9, 127.5, 127.1, 58.5, 53.6, 48.6, 30.2, 21.5, 19.1,
18.1. IR (wmax/cm−1): 3237, 2957, 1441, 1321, 1304,
1153, 1090, 1027, 862, 809, 731, 698, 663, 588, 553, 542
cm−1. FABMS (m/z): 347 (100%) [M+H]. HRMS
(FAB) calcd for C19H27N2O2S [M+H] 347.1793; found:
347.1783.
4.3. General procedure for the preparation of the tert-
iary amine 3 via the double ring opening of the N-
tosyl-aziridines 1 with benzylamine
4.2.2.
N-(2-Benzylamino-1-methylethyl)-4-methylben-
zenesulfonamide 2b. Colourless oil. [h]2D5 −4.8 (c 0.5,
CHCl3). 1H NMR: l 7.79 (d, 2H, J=8.3), 7.39–7.29 (m,
7H), 3.61 (s, 2H,), 3.38–3.25 (m, 1H), 2.51 (dd, 1H,
J=12.4 and 8.1), 2.60 (dd, 1H, J=12.4 and 4.4), 2.43
(s, 3H), 1.13 (d, 3H, J=6.7). 13C NMR: l 143.8, 140.4,
138.1, 130.2, 129.0, 128.5, 127.7, 127.6, 54.3, 53.7, 49.4,
22.1, 20.1. IR (wmax/cm−1): 3266, 2853, 1598, 1494, 1452,
1320, 1156, 1091, 1027, 985, 883, 814, 736, 698, 662,
574, 550. FABMS (m/z): 319 (43%) [M+H]. HRMS
(FAB) calcd for C17H23N2O2S [M+H] 319.1480; found:
319.1485.
All reactions were carried out in an identical manner
and the procedure used is typified by that described for
the preparation of compound 3a as detailed below.
Yields are given in Table 1.
4.3.1. N-(1-{N%-Benzyl-N%-[(2-{4-methylbenzenesulfonyl-
amino}-3-methyl-butyl]aminomethyl}-2-methyl-propyl)-
4-methylbenzenesulfonamide 3a. N-Tosyl-aziridine 1a
(1.6 g, 6.7 mmol,) and benzylamine (0.360 g, 3.35
mmol) were dissolved in dry methanol (30 mL) and the
mixture stirred under reflux for 3 days. The solvent was
evaporated under reduced pressure, leaving an off-
white oil. Upon trituration with diethyl ether (30 mL)
the desired product precipitated as colourless crystals,
which were recrystallised from ethanol in 69% yield
(1.36 g, 2.36 mmol). Mp 135–136°C. [h]2D5 −37.6 (c 0.5,
CHCl3). 1H NMR: l 7.81 (d, 4H, J=8.3), 7.29–7.22 (m,
9H), 5.21 (d, 2H, J=6.7), 3.74 (d, 1H, J=13.3), 3.49–
3.41 (m, 2H), 3.28 (d, 1H, J=13.3), 2.48 (dd, 2H,
J=13.3 and 8.9), 2.41 (s, 6H), 2.32 (dd, 2H J=13.3 and
6.5),1.94–1.78 (m, 2H), 0.66 (t, 12H, J=7.1). 13C NMR:
4.2.3.
N-(1-Benzyl-2-benzylaminoethyl)-4-methylben-
zenesulfonamide 2c. Colourless oil. [h]2D5 −4.0 (c 0.5,
CHCl3). 1H NMR: l 7.68 (d, 2H, J=8.2), 7.34–7.16 (m,
10H), 7.09–7.03 (m, 2H), 3.54 (AB quartet, 2H, J=
13.1), 3.48–3.39 (m, 1H), 2.89 (dd, 1H, J=13.8 and
5.3), 2.73 (dd, 1H, J=13.8 and 8.2), 2.93–2.47 (m, 2H),
2.37 (s, 3H). 13C NMR: l 143.6, 140.3, 137.8, 130.1,
129.8, 128.9, 128.8, 128.4, 127.5, 127.4, 126.9, 54.9,
53.7, 51.5, 40.1, 21.9. IR (wmax/cm−1): 3257, 3027, 1598,
1494, 1453, 1324, 1157, 1092, 960, 814, 743, 700, 664,
631, 533, 503. Anal. calcd for C23H26N2O2S.0.5 H2O: C,

272
J. E. W. Scheuermann et al. / Tetrahedron: Asymmetry 13 (2002) 269–272
l 143.6, 139.2, 138.4, 130.1, 128.9, 127.8, 127.6, 59.0,
56.6, 55.0, 30.1, 22.1, 18.6, 17.7. IR (wmax/cm−1): 3247,
2961, 1599, 1456, 1319, 1184, 1158, 1094, 1074, 1040,
1023, 915, 812, 745, 700, 664, 627, 590, 552, 542, 503,
492. Anal. calcd for C31H43N3O4S2: C, 63.6; H, 7.4;
N, 7.2. Found: C, 63.8; H, 7.4; N, 6.9%. FABMS
(m/z): 586 (47%) [M+H], 359 (100). HRMS (FAB)
calcd for C31H44N3O4S2 [M+H] 586.2773; found:
586.2750.
4.3.5. N-(1-{N%-Benzyl-N%-[(2-{4-methylbenzenesulfonyl-
amino}-3-methyl-pentyl]aminomethyl}-2-methylbutyl)-4-
methylbenzenesulfonamide 3e. Colourless solid. Mp
145–146°C. [h]D25 −15.6 (c 0.5, CHCl3). 1H NMR: l
7.82 (d, 4H, J=8.5), 7.30–7.17 (m, 9H), 5.27 (d, 2H,
J=5.8), 3.75 (d, 1H, J=13.3), 3.58–3.53 (m, 2H),
3.17 (d, 1H, J=13.3), 2.50–2.41 (m, 2H), 2.41 (s, 6H),
2.25 (dd, 2H, J=13.2 and 4.8), 1.63–1.58 (m, 2H),
1.29–1.10 (m, 2H), 1.01–0.88 (m, 2H), 0.80 (t, 6H,
J=7.3), 0.64 (d, 6H, J=7.1). 13C NMR: l 143.3,
139.0, 138.0, 129.8, 129.7, 128.7, 127.6, 127.4, 58.5,
54.9, 53.2, 37.3, 25.5, 21.9, 14.2, 12.5. IR (wmax/cm−1):
3256, 2957, 1597, 1451, 1329, 1300, 1182, 1158, 1123,
1093, 1043, 930, 916, 811, 746, 701, 666, 631, 603,
554, 543. Anal. calcd for C33H47N3O4S2: C, 64.6; H,
7.7; N, 6.9. Found: C, 64.5; H, 8.1; N, 6.5%.
FABMS (m/z): 614 (56%) [M+H], 373 (100). HRMS
(FAB) calcd for C33H48N3O4S2 [M+H] 614.3086;
found: 614.3110.
4.3.2. N-(1-{N%-Benzyl-N%-[(2-{4-methylbenzenesulfonyl-
amino}-propyl]aminomethyl}ethyl)-4-methylbenzenesul-
fonamide 3b. Colourless crystals. Mp 91–92°C. [h]D25
−43.2 (c 0.5, CHCl3). 1H NMR: l 7.79 (d, 4H, J=
8.2), 7.26–7.20 (m, 7H), 7.08–7.04 (m, 2H), 5.08 (d,
2H, J=4.2), 3.56 (d, 1H, J=13.4), 3.48–3.40 (m, 2H),
3.09 (d, 1H, J=13.4), 2.40–2.31 (m, 8H), 2.21 (dd,
2H, J=13.4 and 4.5), 0.94 (d, 6H, J=6.2). 13C
NMR: l 143.3, 138.1, 137.4 129.7, 129.3, 128.5,
127.4, 127.2, 59.5, 57.9, 47.0, 21.6, 19.9. IR (wmax
/
cm−1): 3279, 3225, 2927, 1596, 1494, 1444, 1413, 1345,
1316, 1158, 1092, 1019, 992, 944, 861, 813, 734, 666,
Acknowledgements
591,
572,
553,
533.
Anal.
calcd
for
C27H35N3O4S2·0.5H2O: C, 60.2; H, 7.1; N, 7.8.
Found: C, 60.2; H, 6.7; N, 7.7%. FABMS (m/z): 530
(43%) [M+H], 331 (33). HRMS (FAB) calcd for
C27H36N3O4S2 [M+H] 530.2147; found: 530.2120.
We are grateful to Queen Mary, University of Lon-
don for the provision of
a
PhD studentship
(J.E.W.S.), The Nuffield Foundation for the provision
of an Undergraduate Summer Bursary (G.I.), The
University of London Central Research Fund and
The Royal Society for financial support. We are also
grateful to Dr. K. Welham and Mr. M. Cocksedge of
the School of Pharmacy, University of London for
access to the University of London Inter Collegiate
Research Service (ULIRS) mass spectrometry facility.
4.3.3. N-(1-{N%-Benzyl-N%-[(2-{4-methylbenzenesulfonyl-
amino}-3-phenyl-propyl]aminomethyl}-2-phenyl-ethyl)-4-
methylbenzenesulfonamide 3c. Colourless crystals. Mp
119–120°C. [h]D25 −18.0 (c 0.5, CHCl3). 1H NMR: l
7.63 (d, 4H, J=8.2), 7.20–7.13 (m, 13H), 7.06–7.01
(m, 2H), 6.94–6.91 (m, 4H), 5.22 (bs, 2H), 3.63 (bs,
2H), 3.54 (d, 1H, J=13.5), 3.10 (d, 1H, J=13.5),
2.71 (dd, 2H, J=13.9 and 5.9), 2.55–2.30 (m, 12H).
13C NMR: l 143.2, 138.0, 137.5, 129.7, 129.6, 129.4,
128.6, 128.5, 127.4, 127.1, 126.5, 58.3, 58.0, 53.3,
40.1, 21.6. IR (wmax/cm−1): 3343, 3219, 1599, 1494,
1450, 1415, 1319, 1149, 1090, 1041, 985, 949, 817,
756, 735, 703, 663, 592, 546. FABMS (m/z): 682
(55%) [M+H], 407 (93), 395 (100). HRMS (FAB)
calcd for C39H44N3O4S2 [M+H] 682.2773; found:
682.2750.
References
1. Comprehensive Asymmetric Catalysis; Jacobsen, E. N.;
Pfaltz, A.; Yamamoto, H., Eds.; Springer: Berlin, Heidel-
berg, New York, 1999.
2. Tanner, D. Angew. Chem., Int. Ed. Engl. 1994, 33, 599–
619.
3. (a) Cernerud, M.; Adolfson, H.; Moberg, C. Tetrahedron:
Asymmetry 1997, 8, 2655–2662; (b) Cernerud, M.; Skrin-
ning, A.; Be´rge`re, I.; Moberg, C. Tetrahedron: Asymmetry
1997, 8, 3437–3441; (c) Lake, F.; Moberg, C. Tetrahedron:
Asymmetry 2001, 12, 755–760.
4.3.4. N-(1-{N%-Benzyl-N%-[(2-{4-methylbenzenesulfonyl-
amino}-4-methyl-pentyl]aminomethyl}-3-methyl-butyl)-4-
methylbenzenesulfonamide 3d. Colourless crystals. Mp
112–113°C. [h]D25 −39.6 (c 0.5, CHCl3). 1H NMR: l
7.76 (d, 4H, J=8.2), 7.28–7.15 (m, 9H), 5.13 (bs,
2H), 3.55 (d, 1H, J=13.4), 3.38 (bs, 2H), 3.28 (d, 1H,
J=13.4), 2.48–2.30 (m, 10H), 1.42–1.34 (m, 2H),
1.19–1.14 (m, 4H) 0.72 (d, 6H, J=6.7), 0.62 (d, 6H,
J=6.3). 13C NMR: l 143.2, 138.5, 138.0, 129.6,
128.4, 127.3, 127.1, 59.3, 58.8, 50.3, 43.4, 24.5, 22.8,
22.4, 21.6. IR (wmax/cm−1): 3251, 2950, 1598, 1495,
1452, 1429, 1323, 1305, 1157, 1091, 1041, 1016, 962,
909, 813, 746, 729, 700, 664, 574, 551. Anal. calcd for
C33H47N3O4S2·0.5H2O: C, 63.6; H, 7.7; N, 6.8.
Found: C, 63.7; H, 8.1; N, 6.6%. FABMS (m/z): 614
(32%) [M+H], 373 (100). HRMS (FAB) calcd for
C33H48N3O4S2 [M+H] 614.3086; found: 614.3110.
4. Nelson, S. G.; Peelan, T. J.; Wan, Z. J. Am. Chem. Soc.
1999, 121, 9742–9743.
5. (a) Crabtree, R. H. Chem. Commun. 1999, 1611–1616; (b)
Mun˜iz, K.; Bolm, C. Chem. Eur. J. 2000, 6, 2309–2316.
6. Berry, M. B.; Craig, D. Synlett. 1992, 41–44, neat THF
was used for the reduction of the protected amino acid.
Aziridines 1a and 1c were purified by recrystallisation
from ethanol and all other aziridines were used after
filtration through a short pad of silica gel.
7. Pulacchini, S.; Watkinson, M. Eur. J. Org. Chem. 2001,
4333–4338.
8. Wang, J.-Q.; Zhong, M.; Lin, G.-Q. Chinese J. Org. Chem.
1998, 16, 65–77.