The diastereoselective barbier-type addition to chiral N-tosylimines

Article abstract of DOI:10.1055/s-2003-41453

The Barbier approach was used for diastereoselective formation of allylamino acid derivatives. The stereochemical models for nucleophilic addition to N-tosylimines bearing various chiral auxiliaries such as (2R)-bornano-10,2-sultam, (R)-8-phenylmenthol, a

Full text of DOI:10.1055/s-2003-41453

2110
PRACTICAL SYNTHETIC PROCEDURES
The Diastereoselective Barbier-Type Addition to Chiral N-Tosylimines
Barbier-Type
Add
n
ition to
C
hira
n
l
N
-Tosylim
a
ines Kulesza,a Janusz Jurczak*a,b
a
Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw
b
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw
Fax +48(22)8225996; E-mail: jjurczak@chem.uw.edu.pl
PSP
Received 28 November 2002; revised 3 July 2003
No
8
Abstract: The Barbier approach was used for diastereoselective formation of allylamino acid derivatives. The stereochemical models for
nucleophilic addition to N-tosylimines bearing various chiral auxiliaries such as (2R)-bornano-10,2-sultam, (R)-8-phenylmenthol, and 10-
N,N-dicyclohexylsulfamoyl-(R)-isoborneol are proposed.
Key words: chiral auxiliaries, imines, nucleophilic additions, organometallic reagents, stereoselectivity
Scheme 1
The demand for stereochemically pure, nonproteogenic for the asymmetric induction) connected to the nitrogen
amino acids in pharmaceutical industry triggers intensive atom4,5were also used in the Barbier-type addition.
research effort in this area. The methodology that uses
specifically glyoxyloyl-derived imines for nucleophilic
In our previous reports on the stereoselectivity of N-gly-
oxyloyl-(2R)-bornano-10,2-sultam
in
nucleophilic
addition provides a straightforward route to target amino
acids. Many 1,2-nucleophilic asymmetric additions of or-
ganometallic compounds to chiral imines were exploited
involving Grignard reagents, organozinc compounds, etc.
in enantioselective and diastereoselective ways.1 Recent-
ly, the Barbier reagents were applied for the reactions of
O-alkylated oximes with the assistance of chiral auxilia-
ries.2,3 Imines having the stereogenic center (responsible
addition6 and hetero-Diels–Alder reaction,7,8 we de-
scribed a stereochemical substantiation of asymmetric in-
duction and the benefits of using (2R)-bornano-10,2-
sultam as a chiral auxiliary. 10-N,N-Dicyclohexylsulfa-
moyl-(R)-isobornyl glyoxylate was found less beneficial,
in terms of diastereoselectivity, for the nucleophilic addi-
tion of allyltrimethylsilane to the carbonyl group.9 We
have recently reported the diastereoselective hetero-Di-
els–Alder reaction of N-tosylimine derivatives of N-gly-
oxyloyl-(2R)-bornano-10,2-sultam that showed very high
diastereofacial differentiation.10 Then we focused our at-
tention on nucleophilic addition reactions of allyltrimeth-
Synthesis 2003, No. 13, Print: 18 09 2003. Web: 10 09 2003.
Art Id.1437-210X,E;2003,0,13,2110,2114,ftx,en;T12402SS.pdf.
DOI: 10.1055/s-2003-41453
© Georg Thieme Verlag Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
Barbier-Type Addition to Chiral N-Tosylimines
2111
ylsilane to imines bearing chiral auxilliaries.11,12 In the
present work, we decided to conduct the comparative
studies concerning three different chiral auxiliaries as car-
riers of chirality in the asymmetric Barbier reaction. The
procedure requires mild, nonbasic conditions for the nu-
cleophilic attack and affords high stereoselectivities. The
asymmetric induction in this reaction results from coordi-
nation of the electron lone-pair at nitrogen with zinc; this
can be modulated by chelation with another heteroatom
(C=O, SO2) to form a rigid transition state.
The N-tosylimines were obtained from the corresponding
derivatives of glyoxylic acid using the method introduced
recently by Holmes et al.13 The reaction of compounds
1a,14,15 1b,16–19 and 1c9 with p-toluenesulfonyl isocyanate
(2), in refluxing toluene, afforded the expected imines
3a,10 3b,20 and 3c,12 respectively (Scheme 1). Table 1 pre-
sents the results of the Barbier addition of allylzinc bro-
mide (4) and 2,2-dimethylallylzinc bromide (5) to the
imines 3a–c. The more sterically-demanding zinc deriva-
tive 5 gave the better diastereoselectivities and, in the case
of (R)-8-phenylmenthyl ester 3b, allylamine (S)-7b was
obtained with excellent asymmetric induction. Imines 3a
and 3b, derived from (2R)-bornano-10,2-sultam and 10-
N,N-dicyclohexylsulfamoyl-(R)-isoborneol, respective-
ly, gave relatively low asymmetric inductions. All results
presented in Table 1 confirm the superiority of g-substi-
tuted allyl nucleophiles.
Figure 1 Conformations of chelates A and B derived from 1a.
forced by the cooperative stereoelectronic effect, as
recently formulated by Chapuis et al.7,8for N-glyoxyloyl-
(2R)-bornano-10,2-sultam (1a).
Oppolzer has earlier proposed,23 that the most favorable
conformation was reached when the alkoxy C–H bond
was syn-periplanar to the C=O moiety of the ester (as sup-
ported by recent X-ray analysis).24 As a consequence, all
these groups possess an identical sterically-induced Ca-si
topicity, where the (E)-C=N bond is s-cis to that of the
C=O bond. The PM3 calculations confirmed the thermo-
dynamic stability and higher reactivity of the s-cis over s-
trans conformer for N-benzyl protonated analogues.25
Since the zinc reagent presumably forms the 5-membered
chelate with oxygen and nitrogen (Figure 2), the follow-
ing rationale is proposed. The (R)-8-phenylmenthyl chiral
auxiliary (cf. 1b) provides excellent diastereoselectivities
that hypothetically result from the p-p stacking between
the aryl moiety and the reacting site.26 The pro-R side is
effectively shielded by the aryl moiety. Moreover, the
chelation by zinc additionally stabilizes the transition
state shown below.
Table 1 Results of the Barbier-Type Addition to Chiral Imines
Entry
N-To-
sylimine Reagent (%)
Allylic Yield
Adducts Diastereoisomeric
Ratio of Adducts
C-2¢ (S:R)
1
2
3
4
5
6
3a
3a
3b
3b
3c
3c
4
5
4
5
4
5
46
63
57
50
50
55
6a
7a
6b
7b
6c
7c
60: 40
70: 30
71: 29
100: 0
42: 58
88: 12
Figure 2 Structure of 5-membered Zn-chelate derived from 1b.
In order to rationalize the stereochemical course of allylic
addition to the imine derived from N-glyoxyloyl-(2R)-
bornano-10,2-sultam (1a), we propose two chelates of
type A and B (Figure 1) that lead to opposite diastereoiso-
mers and explain the low diastereoselectivities in entries
1 and 2. The explanation involves an analogy to the pro-
posed rationale for the hetero-Diels–Alder reaction that is
based on two concepts: (a) the sterically controlled ap-
proach of the thermodynamically more stable SO2/CO an-
tiperiplanar, CO/CHNTs s-cis planar conformer A, as
proposed by Oppolzer et al.21and by Curran et al.22 for N-
acryloyl- and N-crotonoyl-(2R)-bornano-10,2-sultam;
and (b) the high reactivity of the less stable SO2/CO syn-
periplanar, CO/CHNTs s-cis planar conformer B, rein-
The configuration 2¢S of the major diastereoisomer 6a and
2¢R of the major diastereoisomer 6c were earlier deter-
mined by X-ray analysis.12 The absolute configuration of
the adduct 6b was obtained by converting the two major
diastereoisomers 6a and 6b, and the minor diastereoiso-
mer 6c to alcohol 8, and comparing the optical rotations of
the respective products (Scheme 2). A similar approach
was used for the series of adducts 7. The configuration 2¢S
of 7a was determined by X-ray analysis (Figure 3). The
absolute configurations of adducts 7b and 7c were ob-
tained by converting all derivatives 7a, 7b and 7c to alco-
hol 9 and comparing the optical rotations of the respective
products (Scheme 2).
Synthesis 2003, No. 13, 2110–2114 © Thieme Stuttgart · New York

2112
A. Kulesza, J. Jurczak
PRACTICAL SYNTHETIC PROCEDURES
glyoxyloyl-(2R)-bornano-10,2-sultam (1a) as well as 10-N,N-dicy-
clohexylsulfamoyl-(R)-isobornyl glyoxylate (1c), and using 10%
EtOAc–hexane as an eluent for the adduct of the imine derived from
(R)-8-phenylmenthyl glyoxylate (1b). The separate diastereoiso-
mers were thus obtained.
N-[(2¢R)-N¢-p-Toluenesulfonylallylglycinoyl]-(2R)-bornano-
10,2-sultam [(R)-6a]
Mp 154–157 °C (hexane–EtOAc); [a]D20 –28.2 (c = 1, CHCl3). All
IR, 1H NMR, 13C NMR, EI-MS, and analytical data were identical
with those obtained by us earlier.12
Scheme 2
N-[(2¢S)-N¢-p-Toluenesulfonylallylglycinoyl]-(2R)-bornano-
10,2-sultam [(S)-6a]
Mp 120–123 °C (hexane–EtOAc); [a]D20 –34.6 (c = 1, CHCl3). All
IR, 1H NMR, 13C NMR, EI-MS, and analytical data were identical
with those obtained by us earlier.12
N-[(2¢S)-N¢-p-Toluenesulfonylallylglycine] 8-(R)-Phenylmen-
thyl Ester [(S)-6b]
1
Oil; [a]D20 +20.6 (c = 1, CHCl3). All IR, H NMR, 13C NMR, EI-
MS, and analytical data were identical with those obtained by us
earlier.12
N-[(2¢R)-N¢-p-Toluenesulfonylallylglycine]-10-N,N-dicyclohex-
ylsulfamoyl (2R)-Isobornyl Ester [(R)-6c]
Mp 171–172 °C; [a]D20 –29.2 (c = 1, CHCl3). All IR, 1H NMR, 13
C
NMR, EI-MS, and analytical data were identical with those ob-
tained by us earlier.12
N-[(2¢S)-N¢-p-Toluenesulfonylallylglycine]-10-N,N-dicyclohex-
ylsulfamoyl (2R)-Isobornyl Ester [(S)-6c]
Figure 3 Crystal Structure of Compound 7a.
Mp 167–168 °C; [a]D20 –14.0 (c = 1, CHCl3). All IR, 1H NMR, 13
C
NMR, EI MS, and analytical data were identical with those obtained
by us earlier.12
The reagent-grade solvents, CH2Cl2, hexanes, EtOAc, THF, were
distilled prior use. All the reported NMR spectra were recorded on
a Varian Gemini spectrometer at 200 MHz (1H NMR) and at 50
MHz (13C NMR). The chemical shifts are reported in d relative to
the TMS signal at d = 0.00 (1H NMR) or d = 0.00 (13C NMR). The
IR spectra were obtained on a Perkin-Elmer 1640 FTIR spectropho-
tometer. The major bands are reported in cm–1. Mass spectra were
obtained on an AMD-604 Intectra instrument using the EI or
LSIMS technique. Chromatography was performed on silica gel
(Kieselgel 60, 200–400 mesh). Optical rotations were recorded us-
ing a Jasco DIP-360 polarimeter with a thermally jacketed 10 cm
cell. All air- or moisture-sensitive reactions were carried out using
flame-dried glassware under argon.
N-[(2¢R)-N¢-p-Toluenesulfonyl-3¢,3¢-dimethylallylglycinoyl]-
(2R)-bornano-10,2-sultam [(R)-7a]
Oil; [a]D20 –29.0 (c = 1, CHCl3).
IR (KBr): 3292, 2962, 2884, 1688, 1339, 1162 cm–1.
1H NMR (200 MHz, CDCl3): d = 7.81 (dAB, J = 8.2 Hz, 2 H), 7.25
(dAB, J = 8.4 Hz, 2 H), 5.97 (m, 1 H), 5.15–4.98 (m, 3 H), 4.23 (br
s, 1 H), 3.74 (br s, 1 H), 3.54–3.28 (m, 2 H), 2.41 (s, 3 H), 2.18–1.83
(m, 5 H), 1.44–1.13 (m, 4 H), 1.09 (s, 3 H), 1.00 (s, 3 H), 0.99–0.82
(m, 5 H).
13C NMR (50 MHz, CDCl3): d = 170.0, 142.4, 129.5, 127.7, 115.5,
60.4, 52.8, 52.2, 47.7, 44.5, 41.1, 38.4, 33.1, 26.3, 24.7, 23.2, 21.6,
20.6, 20.0.
N-Toluenesulfonylimines 3a–c; General Procedure
To a solution of the corresponding glyoxylate (1.5 mmol) in toluene
(10 mL) was added tosyl isocyanate (0.23 mL, 1.5 mmol) under ar-
gon and the reaction mixture was refluxed for 24 h. The obtained
imines were used in situ for allylations.
13C NMR DEPT (50 MHz, CDCl3): d = 142.4 (CH), 129.5 (CH),
127.7 (CH), 115.5 (CH2), 60.4 (CH), 52.8 (CH2), 52.2 (CH), 38.4,
33.1 (CH2), 26.3 (CH2), 24.7, 23.2, 21.6, 20.6, 20.0.
MS (EI): m/z (%) = 1011 ([2 M + Na]+, 100), 517 ([M + Na]+, 10),
425 (42), 252 (48), 155 (94), 91 (100), 69 (42), 41 (29).
Barbier Addition to N-Toluenesulfonylimines 3; General Proce-
dure
HRMS (EI): m/z calcd for C24H34O5N2NaS2 (M + Na): 517.1806;
found: 517.1801.
To a stirred solution of the imine 3 (1 mmol) in toluene in an ice
bath, were added the Barbier reagent 4 or 5 [prepared in situ by re-
acting metallic zinc (126 mg, 2 mmol) and corresponding allyl bro-
mide (1.5 mmol) at 0 °C in THF]. The reaction mixture was stirred
for 12 h at 0 °C. The reaction was quenched by dropwise addition
of 10% HCl. The aqueous phase was extracted with Et2O and the
combined organic extracts were washed with NaHCO3, dried
(MgSO4) and rotary-evaporated under reduced pressure. The prod-
ucts were purified by flash chromatography using 30% Et2O–hex-
ane as an eluent for the adducts of the imines derived from N-
N-[(2¢S)-N¢-p-Toluenesulfonyl-3¢,3¢-dimethylallylglycinoyl]-
(2R)-bornano-10,2-sultam [(S)-7a]
Mp 131–134 °C (hexane–EtOAc); [a]D20 –31.4 (c = 1, CHCl3).
1H NMR (200 MHz, CDCl3): d = 7.82–7.72 (m, 2 H), 7.27–7.19 (m,
2 H), 5.87 (m, 1 H), 5.20–5.01 (m, 3 H), 4.41 (d, J = 10.2, 1 H),
3.75–3.58 (m, 1 H), 3.52–3.28 (m, 2 H), 2.40 (s, 3 H), 2.06–1.80 (m,
5 H), 1.43–0.80 (m, 14 H).
Synthesis 2003, No. 13, 2110–2114 © Thieme Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
Barbier-Type Addition to Chiral N-Tosylimines
2113
13C NMR (50 MHz, CDCl3): d = 171.1, 142.7, 129.9, 129.7, 128.2,
115.8, 62.0, 53.4, 48.4, 48.2, 45.3, 45.2, 42.6, 39.0, 27.0, 26.1, 23.2,
22.2, 21.4, 20.6.
13C NMR DEPT (50 MHz, CDCl3): d = 142.1 (CH), 129.6 (CH),
127.6 (CH), 114.7 (CH2), 81.1 (CH), 64.1 (CH), 57.5 (CH), 54.1
(CH2), 44.2, 39.7 (CH2), 33.5 (CH2), 32.2 (CH2), 30.8 (CH2), 27.0
(CH2), 26.5 (CH2), 26.5 (CH2), 25.2 (CH2), 24.8, 24.2, 21.6, 20.6,
20.3.
X-ray Structural Analysis of (S)-7a
Formula: C24H34N2O5S2, orthorhombic, space group 212121, scan
range 3.24 <2q <20.00, a = 10.650(2), b = 12.450(3), c = 39.010(8)
Å, V = 5172.4(18) Å3, Z = 8, dcalcd = 1.270 Mg·m–3, u = 0.242
mm– 1, 4791 unique reflections, R = 0.0872, Rw = 0.1813.27–30
Reduction of 6a–c and 7a–c; General Procedure
To a stirred solution of 6a, 6b, 6c, 7a, 7b, or 7c (1 mmol) in THF
was added LiAlH4 (76 mg, 2 mmol). After 12 h, the reaction was
quenched with H2O and aq 1 M NaOH, and extracted with CH2Cl2.
The organic layer was dried (MgSO4), and rotary-evaporated. The
product was purified by flash chromatography using 30% EtOAc–
toluene as an eluent. General yield of the products 8 and 9: ca. 80%.
N-[(2¢S)-N¢-p-Toluenesulfonyl-3¢,3¢-dimethylallylglycine) 8-(R)-
Phenylmenthyl Ester [(S)-7b]
Mp 105–107 °C (hexanes–EtOAc); [a]D20 –13.9 (c = 1, CHCl3).
IR (KBr): 3283, 2965, 2928, 1719, 1340, 1163 cm–1.
(2¢S)-N-p-Toluenesulfonylallylglycinol (8)
1H NMR (200 MHz, CDCl3): d = 7.78 (d, J = 8.2 Hz, 2 H), 7.36–
7.10 (m, 5 H), 7.06–6.94 (m, 1 H), 5.51–5.32 (m, 2 H), 4.98–4.08
(m, 2 H), 4.42 (td, J1 = 4.0 Hz, J2 = 10.6 Hz, 1 H), 3.10 (d, J = 9.8
Hz, 1 H), 2.42 (s, 3 H), 2.04–1.84 (m, 2 H), 1.70–1.53 (m, 2 H),
1.50–1.28 (m, 1 H), 1.00 (s, 3 H), 0.91 (s, 3 H), 0.90–0.75 (m, 11 H).
13C NMR (50 MHz, CDCl3): d = 169.7, 151.8, 143.3, 142.8, 137.1,
129.5, 127.9, 127.3, 125.1, 125.0, 113.3, 62.4, 50.5, 40.8, 40.6,
39.1, 34.4, 31.2, 27.5, 26.4, 25.0, 24.2, 23.1, 21.6, 21.5.
13C NMR DEPT (50 MHz, CDCl3): d = 142.8 (CH), 129.5 (CH),
127.9 (CH), 127.3 (CH), 125.1 (CH), 125.0 (CH), 113.3 (CH2), 62.4
(CH), 50.5 (CH), 40.8 (CH2), 40.6, 34.4 (CH2), 31.2, 27.5, 26.4
(CH2), 25.0, 24.2, 23.1, 21.6, 21.5.
Mp 40–43 °C (hexanes–EtOAc); [a]D20 +17.0 (c = 1, CHCl3). All
IR, 1H NMR, 13C NMR, EI-MS, and analytical data were identical
with those obtained by us earlier.12
(2¢S)-N-p-Toluenesulfonyl-3¢,3¢-dimethylallylglycinol (9)
Mp 115–118 °C (hexanes–EtOAc); [a]D20 +3.2 (c = 1, CHCl3).
1H NMR (200 MHz, CDCl3): d = 7.77 (dAB, J = 8.4 Hz, 2 H), 7.31
(dAB, J = 8.4 Hz, 2 H), 5.66 (m, 1 H), 5.05–4.95 (m, 2 H), 4.78 (d,
J = 8.4 Hz, 1 H), 3.57 (d, J = 8.4 Hz, 1 H), 3.08–2.98 (m, 1 H), 2.43
(s, 3 H), 0.97 (s, 3 H), 0.90 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 144.0, 137.3, 129.7, 127.3, 114.1,
66.1, 62.5, 24.5, 23.9, 22.0, 21.6.
ESI: m/z (%) = 1045 ([2M + Na]+, 100), 795 ([M + Na]+, 3).
HRMS (EI): m/z calcd for C14H21NNaO3S (M + Na): 306.1134;
found: 306.1152.
HRMS (EI): m/z calcd for C33H50O4N2S1Na (M + Na): 534.2615;
found: 534.2615.
Anal. Calcd for C14H21NNaO3S: C, 59.4; H, 7.4; N, 5.0; S, 11.3.
Found: C, 59.3; H, 7.5; N, 4.8; S, 11.3.
Anal. Calcd for C33H50N2NaO4S: C, 70.5; H, 8.0; N, 2.7; S, 6.3.
Found: C, 70.2; H, 8.2; N, 2.8; S, 6.2.
Acknowledgment
N-[(2¢R)-N¢-p-Toluenesulfonyl-3¢,3¢-dimethylallylglycine]-10-
N,N-dicyclohexylsulfamoyl (2R)-Isobornyl Ester [(R)-7c]
Oil; [a]D20 –14.8 (c = 1, CHCl3).
This work was supported by Polish State Committee for Scientific
Research, Grant PBZ 6.05/T09/1999.
1H NMR (200 MHz, CDCl3): d = 7.71 (dAB, J = 8.2 Hz, 2 H), 7.29
(dAB, J = 8.2 Hz, 2 H), 5.80 (m, 1 H), 5.08–4.93 (m, 3 H), 4.63
(qAB, J1 = 3.4 Hz, J1 = 7.8 Hz, 1 H), 3.94 (d, J = 9.8 Hz, 1 H), 3.40–
3.20 (m, 3 H), 2.70 (dAB, J = 13.4 Hz, 1 H), 2.39 (s, 3 H), 2.10–1.20
(m, 29 H), 1.16 (s, 3 H), 1.09 (s, 3 H), 0.97 (s, 3 H), 0.88 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 169.7, 143.4, 143.0, 137.7, 129.8,
127.0, 114.2, 81.7, 64.2, 57.6, 53.9, 49.6, 489.0, 44.2, 40.8, 39.7,
33.3, 32.5, 30.8, 26.8, 26.5, 26.3, 25.3, 25.1, 23.6, 21.5, 20.5, 20.5.
References
(1) Denmark, S. E.; Nicaise, O. J.-C. Comprehensive
Asymmetric Catalysis II; Springer: New York, 1999, 924.
(2) Hanessian, S.; Yang, R. Y. Tetrahedron Lett. 1996, 37,
5273.
(3) Yamamoto, Y.; Ito, W. Tetrahedron 1988, 44, 5415.
(4) Bocoum, A.; Savoia, D.; Umani-Ronchi, A. J. Chem. Soc.,
Chem. Commun. 1993, 1542.
(5) Basile, T.; Savoia, D.; Umani-Ronchi, A. J. Org. Chem.
1994, 59, 7766.
(6) Kiegiel, K.; Jurczak, J. Tetrahedron Lett. 1999, 40, 1009.
(7) Bauer, T.; Chapuis, C.; Jeżewski, A.; Kozak, J.; Jurczak, J.
Tetrahedron: Asymmetry 1996, 7, 1391.
(8) Chapuis, C.; Laumer, J.-V. S.; Marty, M. Helv.Chim. Acta
1997, 80, 146.
(9) Czapla, A.; Chajewski, A.; Bauer, T.; Wielogórski, Z.;
Urbańczyk-Lipkowska, Z.; Jurczak, J. Tetrahedron:
Asymmetry 1999, 10, 2101.
(10) Bauer, T.; Szymański, S.; Jeżewski, A.; Gluziński, P.;
Jurczak, J. Tetrahedron: Asymmetry 1997, 8, 2619.
(11) Kulesza, A.; Jurczak, J. Chirality 2001, 13, 634.
(12) Kulesza, A.; Mieczkowski, A.; Jurczak, J. Tetrahedron:
Asymmetry 2002, 13, 2061.
MS (EI): m/z (%) = 699 ([M + Na]+, 100), 677([M + H]+, 30), 380
(15), 91 (47), 84 (100), 47 (19).
HRMS (EI): m/z calcd for C36H56N2NaO6S2 (M + Na): 699.3509;
found: 699.3472.
Anal. Calcd for C36H56N2NaO6S2: C, 63.9; H, 8.3; N, 4.1; S, 9.5.
Found: C, 63.5; H, 8.4; N, 4.1; S, 9.7.
N-[(2¢S)-N¢-p-Toluenesulfonyl-3¢,3¢-dimethylallylglycine]-10-
N,N-dicyclohexylsulfamoyl (2R)-Isobornyl Ester [(S)-7c]
Oil; [a]D20 –36.1 (c = 1, CHCl3).
1H NMR (200 MHz, CDCl3): d = 7.72 (dAB, J = 7.9 Hz, 2 H), 7.26
(dAB, J = 7.9 Hz, 2 H), 5.85 (m, 1 H), 5.47 (d, J = 9.8 Hz, 1 H),
5.16–5.00 (m, 2 H), 4.59 ((qAB, J1 = 3.2 Hz, J1 = 7.6 Hz, 1 H), 3.51
(d, J = 9.8 Hz, 1 H), 3.35–3.19 (m, 2 H), 3.15 (dAB, J = 13.6 Hz, 2
H), 2.64 (dAB, J = 13.4 Hz, 2 H), 2.40 (s, 3 H), 2.05–1.26 (m, 26
H), 1.17 (s, 6 H), 1.10–0.88 (m, 3 H), 0.84 (s, 6 H).
(13) Hamley, P.; Holmes, A. B.; Kee, A.; Ladduwahetty, T.;
Smith, D. F. Synlett 1991, 29.
(14) Bauer, T.; Chapuis, C.; Kozak, J.; Jurczak, J. Helv. Chim.
Acta 1989, 72, 482.
13C NMR (50 MHz, CDCl3): d = 169.4, 143.5, 142.1, 137.1, 129.6,
127.6, 114.7, 81.1, 64.1, 57.5, 54.1, 49.4, 49.3, 44.2, 40.0, 39.7,
33.5, 32.2, 30.8, 27.0, 26.5, 26.5, 25.2, 24.8, 24.2, 21.6, 20.6, 20.3.
Synthesis 2003, No. 13, 2110–2114 © Thieme Stuttgart · New York

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A. Kulesza, J. Jurczak
PRACTICAL SYNTHETIC PROCEDURES
(15) Bauer, T.; Chapuis, C.; Kozak, J.; Jurczak, J. J. Chem. Soc.,
Chem. Commun. 1990, 1178.
(25) Szymański, S.; Chapuis, C.; Jurczak, J. Tetrahedron:
Asymmetry 2001, 12, 1939.
(16) Whitesell, J. K.; Bhattacharya, A.; Aguilar, D. A.; Henke, K.
J. Chem. Soc., Chem. Commun. 1982, 989.
(17) Whitesell, J. K.; Bhattacharya, A.; Buchanan, C.; Chen, H.
H.; Deyo, D.; James, D.; Liu, C. L.; Minton, M. A.
Tetrahedron 1986, 42, 2993.
(18) Yamamoto, Y.; Ito, W. Tetrahedron 1988, 44, 5415.
(19) Freund, R.; Mahboobi, S.; Noack, K.; Schoenholzer, P.;
Bernauer, K. Helv. Chim. Acta 1990, 73, 439.
(20) Ge, C. S.; Chen, Y. J.; Wang, D. Synlett 2002, 37.
(21) Oppolzer, W.; Poli, G.; Starkeman, C.; Bernardinelli, G.
Tetrahedron Lett. 1988, 29, 3559.
(22) Curran, D. P.; Kim, B. H.; Daugherty, J.; Heffner, T. A.
Tetrahedron Lett. 1988, 29, 3555.
(23) Oppolzer, W.; Chapuis, C.; Mao Dao, G.; Rechlin, D.;
Godel, T. Tetrahedron Lett. 1982, 23, 4781.
(24) Blnco, J. M.; Caamano, O.; Fernandez, F.; Garcia-Mera, X.;
Lopez, C.; Rodriguez, G.; Rodriguez-Borgez, J. E.;
Rodriguez-Hergueta, A. Tetrahedron Lett. 1998, 39, 5663.
(26) Kober, R.; Papadopoulos, K.; Miltz, W.; Enders, D.;
Steglich, W.; Reuter, H.; Puff, H. Tetrahedron 1985, 41,
1693.
(27) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(28) Sheldrick, G. M. SHELX-93: Program for the Refinement of
Crystal Structures; University of Göttingen: Germany,
1993.
(29) Crystallography, Vol. C; Wilson, A. J. C., Ed.; Kluwer:
Dordrecht, 1992.
(30) The crystallographic data for the structure reported in this
paper have been deposited with the Cambridge
Crystallographic Data Center as supplementary publication
no. CCDC-194392. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK [fax (+44)1223336033; e-mail:
deposit@ccdc.cam.ac.uk].
Synthesis 2003, No. 13, 2110–2114 © Thieme Stuttgart · New York