6466
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raphy (silica gel: EtOAc/hexane) to yield aziridine peptide
5 (67%), [h]2D5 −139.7 (c 0.018, CH2Cl2). A solution of
1.10–0.80 (m, 6H). Mass (m/z, CI): 520 (M++1), 472, 374,
243, 182.
aziridine peptide 5 (200 mg, 0.52 mmol) and triethylamine
(145 mL, 1.02 mmol) in DCM (5 mL) was cooled to 0°C and
to it was added cinnamoyl chloride (86 mg, 0.52 mmol) in
DCM (3 mL). The solution was warmed to room tempera-
ture and stirred for 6 h. The solvent was removed and the
residue was taken in EtOAc (10 ml) and washed with
saturated solution of NaHCO3 (2×10 mL) and brine (10
mL). The organic phase was dried (Na2SO4) and concen-
trated to give a residue which was subjected to flash
chromatography (silica gel: EtOAc/Pet ether) to yield the
7. Synthetic protocols: Compound 8 and 9: To a stirred
solution of trimethylsilyl chloride (43 mL, 337 mmol) in
acetonitrile (10 mL) sodium iodide (50.7 mg, 338 mmol) was
added under nitrogen and it was stirred at room temperature
until the solution turned yellow. A solution of aziridine 6
(100 mg, 193 mmol) in acetonitrile (5 mL) was added to the
above mixture and refluxed for 5 h. The reaction mixture
was cooled down to room temperature and Et3N (54 mL, 384
mmol) was added to it and was stirred at room temperature
for further 6 h. The solvent and reagents were removed and
the residue was purified by column chromatography (silica
gel: EtOAc/Pet ether) to afford the oxazoline 8 (60%). This
intermediate 8 (60 mg) in acetonitrile (7 mL) was mixed with
Me3SiCl (25 mL, 197 mmol), NaI (30 mg, 197 mmol) and
refluxed for 15 h. The usual work up (as described for 8)
afforded the pure compound 9 (60%).
1
peptide 6 (50%), [h]D25 −19.4 (c 0.5, CHCl3). H NMR (200
MHz, CDCl3): l 7.76 (d, J=7.0 Hz, NH), 7.68 (d, J=16.1
Hz, 1H), 7.52–7.29 (m, 10H), 7.03 (d, J=7.8 Hz, NH
unbound), 6.62 (d, J=16.0 Hz, 0.5H), 6.56 (d, J=16.0 Hz,
0.5H), 4.71–4.45 (m, 2H), 4.26 (d, J=2.0 Hz, 0.5H), 4.07
(d, J=2.0 Hz, 0.5H), 3.80–3.60 (m, 5H), 3.36 (d, J=2.0 Hz,
0.5H), 3.29 (d, J=2.0 Hz, 0.5H), 2.60–1.50 (m, 7H),
1.00–0.84 (m, 6H). Mass (m/z, CI): 518 (M++1), 391, 345,
311, 257, 243, 148, 131, 107.
Spectral data of 8: 1H NMR (200 MHz, CDCl3): l 7.58–7.34
(m, 11H), 7.16 (d, J=7.8 Hz, NH), 6.70 (d, J=16.1 Hz, 1H),
6.14 (d, J=7.3 Hz, 1H), 4.79 (d, J=7.3 Hz, 1H), 4.62–4.10
(m, 2H), 3.72–3.43 (m, 5H), 2.40–2.20 (m, 1H), 2.13–1.91
(m, 3H), 1.74–1.54 (m, 3H), 0.96–0.84 (m, 6H). Mass (m/z,
CI): 518 (M++1), 431, 373, 345, 248, 209, 119.
6. Synthetic protocols: Compound 7: To a solution of aziridine
6 (110 mg, 0.212 mmol) in dry THF (8 mL) NaCNBH3 (27
mg, 0.43 mmol) and p-TsOH (5 mol%) were added and
stirred at room temperature for 14–15 h. The solvent was
removed and the residue was dissolved in ether. The organic
layer was washed with brine (10 mL) followed by water (10
mL). Drying and evaporation of ether gave a residue, which
was chromatographed over silica gel to afford the tripeptide
1
Spectral data of 9: H NMR (200 MHz, CDCl3): l 7.86 (s,
NH bound), 7.60 (d, J=15.6 Hz, 1H), 7.50–7.20 (m, 10H),
6.55 (d, J=15.6 Hz, 1H), 6.12 (s, 1H), 4.69–4.45 (m, 2H),
3.80–3.58 (m, 5H), 2.40–2.20 (m, 1H), 2.13–1.54 (m, 6H),
1.00–0.75 (m, 6H). Mass (m/z, CI): 518 (M++1), 372, 276,
243, 131.
1
7 (45.5%). The H NMR and specific rotation of 7 ([h]D25
8. For b-turn see: (a) Ball, J. B.; Hughes, R. A.; Alewood, P.
L.; Andrews, P. R. Tetrahedron 1993, 49, 3467 and refer-
ences cited therein; (b) Haubner, R.; Finsinger, D.; Kessler,
H. Angew. Chem., Int. Ed. Engl. 1997, 36, 1374; (c) Kim. K.;
Germanas, J. P. J. Org. Chem. 1997, 62, 2853; (d) Jones, I.
G.; Jones, W.; North, M. J. Org. Chem. 1998, 63, 1505; (e)
Krauthauser, S.; Christianson, L. A.; Powell, D. R.; Gell-
man, S. H. J. Am. Chem. Soc. 1997, 119, 11719.
−37.9 (c 0.19, CHCl3) were similar to the authentic
tripeptide [h]2D5 −44.6 (c 0.19, CHCl3) prepared from N-cin-
namoyl
L-Phe, L-Pro and L
-Leu. 1H NMR (200 MHz,
CDCl3): l 8.07 (d, J=7.0 Hz, NH), 7.61 (d, J=16.1 Hz, 1H),
7.55–7.20 (m, 10H), 7.03 (d, J=7.3 Hz, NH), 6.39 (d,
J=15.6 Hz, 1H), 5.11 (d, J=7.3 Hz, 1H), 4.62–4.43 (m, 2H),
3.75 (s, 3H), 3.70–3.50 (m, 2H), 3.10 (d, J=4.9 Hz, 2H),
2.38–2.20 (m, 1H), 2.00–1.80 (m, 2H), 1.80–1.50 (m, 4H),