G. Reginato et al. / Tetrahedron 61 (2005) 6791–6800
6799
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Compound (17b): H NMR (400 MHz) d: 0.90 (0.93) [d,
JZ6.8 Hz, 3H]; 1.40 (1.41) [s, 9H]; 2.19–2.40 [m, 1H];
2.66–2.97 [m, 2H]; 3.16–3.32 [m, 1H]; 3.33–3.48 [m, 1H];
4.27–4.33 [br Fm, 1H]; 4.57 [br d, 1H]; 5.33–5.24 (5.31–
5.21) [m, JABZ15.4, JBXZ7.4 Hz, 1H]; 5.34–5.49 [m,
JABZ15.4, JAXZ6.2 Hz, 1H]; 7.40–7.10 [m, 5H]. 13C
NMR (50.3 MHz) d: 16.04 (16.15); 24.57; 28.32; 39.44;
41.60 (41.67); 53.78; 66.94; 79.50; 126.50; 128.34; 129.49;
131.01 (131.22); 137.61 (137.86); 155.18 (155.27). MS m/z
(%): 158 (43); 91 (92); 56 (100). Anal. Calcd for
C18H27NO3: C, 70.79; H, 8.91; N. 4.59. Found: C, 70.64;
H, 8.77; N, 4.63.
References and notes
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4.6.2. Oxidation: general procedure. A stock solution of
H5IO6 (0.4 M, 2.5 equiv) and CrO3 (0.5% mol) in wet
acetonitrile was added dropwise to a cooled solution of
amino alcohols 17a,b in wet acetonitrile. The reaction
mixture was stirred for 30 min. then quenched with
phosphate buffer. After dilution with ethyl acetate the
organic layer was separated, washed with brine/aqueous
NaHSO3 (0.4 M)/brine and then dried. Crude acids 19a,b
were dissolved in CH2Cl2, cooled at 0 8C and reacted with
(L)-phenylalanine methyl ester (1.5 equiv), DIPEA
(3 equiv) and diethylcyanophosphonate at room tempera-
ture overnight. Dilution with ethyl acetate, washing with
water and evaporation afforded crude 20a,b which were
purified by flash chromatography.
7. Spatola, A. F. In Chemistry and biochemistry of amino acids,
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4.6.2.1. Boc-Gly-j-[(E)-CH]CH]-(rac)-Ala-(S)-Phe-
OMe (19a). Oxidation of 17a (67 mg, 0.3 mmol) and
coupling with (L)-phenylalanine methyl ester (94 mg,
0.45 mmol) gave, after purification [petroleum ether/ethyl
acetateZ1:3], 19a (53 mg, 44%) as a white solid.
16. Jenmalm, A.; Berta, W.; Li, Y.-L.; Luthman, K.; Csoregh, I.;
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Compound (19a): 1H NMR (200 MHz) d: 1.22 (1.23) [d, JZ
7.0 Hz, 3H]; 1.45 (1.46) [s, 9H]; 2.83–3.00 [m, 1H]; 3.04–
3.19 [m, 2H]; 3.64–3.75 [m, 2H]; 3.73 [s, 3H]; 4.53 [br s,
1H]; 4.76–5.89 [m, 1H]; 5.51–5.60 [m, 2H]; 6.01 [br s, 1H];
7.03–7.19 [m, 5H]. 13C NMR (50.3 MHz) d: 17.57; 28.42;
32.54; 42.31; 43.90; 52.87 (52.34); 55.97; 79.28; 127.11;
128.47; 129.22; 129.49; 131.53; 136.22; 156.12; 171.89;
173.34.
18. Ibuka, T.; Mimura, N.; Ohno, H.; Nakai, K.; Akajii, M.;
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4.6.2.2. Boc-(L)Phe-j-[(E)-CH]CH]-(rac)-Ala-(S)-
Phe-OMe (19b). Oxidation of 17b (63 mg, 0.20 mmol)
and coupling with (L)-phenylalanine methyl ester (83 mg,
0.43 mmol) gave, after purification [petroleum ether/ethyl
acetateZ1:3], 19b (46 mg, 48%) as a white solid.
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Compound (19b): 1H NMR (200 MHz) d: 1.16 [d, JZ
6.8 Hz, 3H]; 1.40 (1.39) [s, 9H]; 2.76–3.19 [m, 2HC1HC
2H]; 3.72 [s, 3H]; 4.22–4.47 [mC br s, 1HC1H]; 4.67–4.76
[m, 1H]; 5.46–5.12 [m, 2H]; 6.03 [br s, 1H]; 7.03–7.29 [m,
10H]. 13C NMR (50.3 MHz) d: 173.32; 171.92; 155.04;
137.25; 135.99; 132.53; 130.13; 129.47; 129.24; 128.45;
128.34; 127.03; 126.47; 79.49; 53.11; 52.98; 52.29; 43.93
(43.86); 41.51; 37.73; 28.39; 17.13 (16.97).
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Acknowledgements
30. Reginato, G.; Mordini, A.; Caracciolo, M. J. Org. Chem. 1997,
62, 6187.
Ente Cassa di Risparmio di Firenze (Italy) is acknowledged
for granting a 400 MHz NMR spectrometer.
31. Reginato, G.; Mordini, A.; Degl’Innocenti, A.; Manganiello,
S.; Capperucci, A.; Poli, G. Tetrahedron 1998, 54, 10227.