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Helvetica Chimica Acta – Vol. 90 (2007)
(3 ml) was added dropwise. Then, the temp. was slowly raised to 08, and the mixture was stirred for ca. 6 h
(TLC control). After completion of the reaction, the mixture was quenched with 2m aq. HCl (10 ml) and
washed with sat. aq. NaHCO3 soln. (3 ꢁ 10 ml) and H2O (10 ml). The org. layer was dried (MgSO4) and
concentrated. The crude product was purified by CC (silica gel, petroleum ether/AcOEt 8 :1):
diaminonitrile 4a or 4b as white solid.
(2R,3R)-3-{[(tert-Butoxy)carbonyl]amino}-4-phenyl-2-[(2,3,4,6-tetra-O-pivaloyl-b-d-glucopyrano-
syl)amino]butanenitrile (4a). Prepared according to GP 2: 4a (0.703 g, 91% from 1). White solid. M.p.
102 – 1048. [a]2D0 ¼ ꢀ19.3 (c ¼ 1.0, CHCl3). IR (KBr): 3444, 2977, 2247, 1744, 1631, 1481, 1460, 1146, 1033,
1
762, 700. H-NMR (500 MHz, CDCl3): 7.22 – 7.34 (m, 5 H); 5.35 (t, J ¼ 9.6, 1 H); 5.11 (t, J ¼ 9.6, 1 H);
4.88 (t, J ¼ 9.6, 1 H); 4.71 (d, J ¼ 6.8, 1 H); 4.18 – 4.24 (m, 3 H); 4.02 – 4.05 (m, 1 H); 4.00 (d, J ¼ 4.4,
1 H); 3.68 (dd, J ¼ 3.6, 6.0, 1 H); 2.90 (d, J ¼ 7.2, 2 H); 2.62 (s, 1 H); 1.67 (s, 1 H); 1.12 – 1.54 (m, 45 H).
13C-NMR (125 MHz, CDCl3): 178.0; 177.5; 177.0; 176.4; 135.9; 129.0; 128.8; 127.2; 117.7; 87.3; 80.5; 73.4;
72.3; 70.3; 67.7; 61.6; 50.7; 38.8 – 38.1; 28.2 – 26.9. HR-MS: 774.4536 ([M þ H]þ, C41H64N3O1þ1 ; calc.
774.4541).
(2R,3S)-3-{[(tert-Butoxy)carbonyl]amino}-4-phenyl-2-[(2,3,4,6-tetra-O-pivaloyl-b-d-glucopyrano-
syl)amino]butanenitrile (4b). Prepared according to GP 2: 4b (0.692 g, 89% from 1). White solid. M.p.
109 – 1128. [a]2D0 ¼ ꢀ4.3 (c ¼ 1.2, CHCl3). IR (KBr): 3450, 2977, 2245, 1744, 1631, 1481, 1460, 1146, 1036,
1
760, 698. H-NMR (500 MHz, CDCl3): 7.21 – 7.33 (m, 5 H); 5.34 (t, J ¼ 9.6, 1 H); 5.10 (t, J ¼ 9.6, 1 H);
4.87 (t, J ¼ 9.6, 1 H); 4.72 (d, J ¼ 6.8, 1 H); 4.17 – 4.23 (m, 3 H); 4.02 – 4.04 (m, 1 H); 3.99 (d, J ¼ 5.2,
1 H); 3.67 (dd, J ¼ 3.2, 6.4, 1 H); 2.89 (d, J ¼ 7.2, 2 H); 2.62 (s, 1 H); 1.82 (s, 1 H); 1.11 – 1.53 (m, 45 H).
13C-NMR (125 MHz, CDCl3): 178.0; 177.5; 176.9; 176.3; 135.9; 129.0; 128.8; 127.1; 117.6; 87.2; 80.4; 73.3;
72.3; 70.3; 67.7; 61.6; 50.7; 38.8; 38.7; 38.6; 38.0; 28.1; 27.2; 27.1; 27.0. HR-MS: 774.4539 ([M þ H]þ,
C41H64N3Oþ11 ; calc. 774.4541).
2,3-Diamino-4-phenylbutanoic Acid Dihydrochlorides 5a and 5b: General Procedure 3 (GP 3). Anh.
HCl gas was bubbled through a soln. of 4 (0.660 g , 1.0 mmol) in formic acid (20 ml) for 24 h at r.t. Then,
the soln. was concentrated and filtered over silica gel (20 g), eluting with light petroleum ether/AcOEt
1:1. The silica gel (containing the product) was dried, and repeatedly extracted with 2n aq. HCl (400 ml).
The combined acidic soln. was concentrated to ca. 10 ml, diluted with conc. HCl (10 ml), and heated to
808 for 48 h. After evaporation, 2,3-diamino-4-phenylbutanoic acid dihydrochloride 5a or 5b was
obtained.
(2R,3R)-2,3-Diamino-4-phenylbutanoic Acid Dihydrochloride (5a). Prepared according to GP 3: 5a
(0.226 g, 99%). White crystalline solid. M.p. 171 – 1728. [a]2D0 ¼ ꢀ1.8 (c ¼ 1.04, MeOH) ([16]: [a]2D0
¼
1
ꢀ1.8, c ¼ 1.3, MeOH). IR (KBr): 3478 – 2500 (br.), 1685, 1629, 1496, 1456, 1401. H-NMR (500 MHz,
D2O): 7.22 – 7.37 (m, 5 H); 4.08 (d, J ¼ 5.2, 1 H); 3.99 (m, 1 H); 3.19 (dd, J ¼ 14.4, 5.2, 1 H); 2.97 (dd, J ¼
14.5, 10.2, 1 H). 13C-NMR (125 MHz, D2O): 167.1; 133.6; 129.4; 128.9; 127.6; 55.2; 52.9; 35.5. HR-MS:
98.0632 ([M þ 2 H]2þ, C10H16N2O22þ ; calc. 98.0606).
(2R,3S)-2,3-Diamino-4-phenylbutanoic Acid Dihydrochloride (5b). Prepared according to GP 3:
anti-5b (0.223 g, 98%). White crystalline solid. M.p. 206 – 2088. [a]2D0 ¼ ꢀ18.7 (c ¼ 0.34, MeOH) ([16]:
[a]2D0 ¼ ꢀ18.8, c ¼ 1.4, MeOH). IR (KBr): 3450 – 2500(br), 1687, 1631, 1496, 1456, 1401. 1H-NMR
(500 MHz, D2O): 7.15 – 7.26 (m, 5 H); 4.21 (d, J ¼ 3.2, 1 H); 4.07 (d, J ¼ 10.8, 1 H); 3.08 (dd, J ¼ 13.6,
3.2, 1 H); 2.82 (dd, J ¼ 13.8, 11.6, 1 H). 13C-NMR (125 MHz, D2O): 166.4; 132.8; 128.7; 128.4; 127.5; 61.0;
52.8; 35.7. HR-MS: 98.0627 ([M þ 2 H]2þ, C10H16N2O22þ ; calc. 98.0606).
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