N. Duguet et al. / Tetrahedron: Asymmetry 21 (2010) 601–616
615
dance with the literature4 and as described above. HPLC analysis:
3% ee.
Me
O
N
Acknowledgements
O
S
O
The authors would like to thank the Royal Society for a Univer-
sity Research Fellowship (ADS), The Leverhulme Trust (ND), Pfizer
(CASE award to SML), GlaxoSmithKline (CASE award to AD), and
The Carnegie Trust for the Universities of Scotland (CDC) for fund-
ing. Prof. Nigel Simpkins is gratefully acknowledged for the gener-
ous gift of an authentic sample of diamine 17. The EPSRC mass
spectrometry facility is also acknowledged.
Et
O
Ph
5.7.4. Scheme 8 entry 6: (3R,4R)-3-ethyl-4-(furan-2-yl)-3-
phenyl-1-tosylazetidin-2-one (3R,4R)-25
The b-lactam (3R,4R)-25 was prepared using ethylphenylketene
(45.2 mg, 0.309 mmol) and N-(2-furfurylidene)-4-methylbenzene-
sulfonamide (59.4 mg, 0.238 mmol) with chiral imidazolinium salt
35 (11.2 mg, 0.0238 mmol) and a 0.50 M solution of KHMDS in
toluene (0.04 mL, 0.0214 mmol) following the above-mentioned
general procedure. The crude product was purified by silica chro-
matography (EtOAc/petrol 5:95 then EtOAc/petrol 10:90) to give
b-lactam (3R,4R)-25 as a pale yellow solid (31.9 mg, 34%) and as
a diastereomeric mixture (dr syn:anti 65:35) with spectroscopic
data in accordance with the literature4 and as described above.
HPLC analysis: 4% ee.
References
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Et
O
Ph
5.7.5. Scheme 8 entry 7: (3R,4R)-3-ethyl-4-(furan-2-yl)-3-
phenyl-1-tosylazetidin-2-one (3R,4R)-25
The b-lactam (3R,4R)-25 was prepared using ethylphenylketene
(38.2 mg, 0.261 mmol) and N-(2-furfurylidene)-4-methylbenzene-
sulfonamide (50.1 mg, 0.201 mmol) with chiral imidazolinium salt
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meric mixture (dr syn:anti 70:30) with spectroscopic data in accor-
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0% ee.
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5.7.6. Scheme 8 entry 8: (3R,4R)-3-ethyl-4-(furan-2-yl)-3-
phenyl-1-tosylazetidin-2-one (3R,4R)-25
The b-lactam (3R,4R)-25 was prepared using ethylphenylketene
(38.2 mg, 0.261 mmol) and N-(2-furfurylidene)-4-methylbenzene-
sulfonamide (50.1 mg, 0.201 mmol) with chiral imidazolinium salt
39 (4.7 mg, 0.020 mmol) and a 0.50 M solution of KHMDS in tolu-
ene (0.04 mL, 0.018 mmol) following the above-mentioned general
procedure. The crude product was purified by silica chromatogra-
phy (EtOAc/petrol 10:90 then EtOAc/petrol 30:70) to give b-lactam
(3R,4R)-25 as a pale yellow solid (67.8 mg, 76%) and as a diastereo-
meric mixture (dr syn:anti 68:32) with spectroscopic data in accor-
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16. The absolute configuration of the major syn-diastereoisomer 25 was
established by comparison of the sign of its specific rotation ½a D20
¼ ꢀ30 (c
ꢁ
0.1, CH2Cl2) to the literature,4a a 2D5
½ ꢁ ¼ ꢀ45:2 (c 0.5, CH2Cl2).