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M. T. Bartolomé et al. / Tetrahedron: Asymmetry 9 (1998) 249–258
159.8, 147.0, 145.4, 134.9, 130.5, 127.8, 127.1, 127.0, 126.3, 120.6, 114.6, 68.6, 55.4, 52.9, 48.5, 27.7,
18.5. Analysis calc. for C22H21N3O4: C, 67.51; H, 5.41; N, 10.74. Found: C, 67.81; H, 5.40; N, 10.69.
1.5. (1R,4S)-2-Benzyl-4-methyl-1-pivaloyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-dione 2c
1
Mp: 128°C (ethyl ether). IR (KBr) ν: 1718, 1686, 1596 cm−1. H-NMR (CDCl3) δ: 8.25 (1H, dd,
J=8.0, 1.5 Hz, H-7), 7.74 (1H, ddd, J=8.2, 7.1, 1.5 Hz, H-9), 7.60 (1H, dd, J=8.2, 1.2 Hz, H-10), 7.49
(1H, ddd, J=8.0, 7.1, 1.2 Hz, H-8), 7.33 (3H, m, ArH), 7.25 (2H, m, ArH), 5.61 (1H, s, H-1), 5.37 (1H,
q, J=7.1 Hz, H-4), 5.18 (1H, d, J=15.0 Hz, Ar–CH2–N), 3.97 (1H, d, J=15.0 Hz, Ar–CH2–N), 1.73 (3H,
d, J=7.1 Hz, CH3), 1.16 (9H, s, 3CH3). 13C-NMR (CDCl3) δ: 208.8, 169.4, 160.3, 146.7, 146.4, 134.9,
134.6, 129.2, 128.9, 128.5, 127.7, 127.1, 126.9, 120.5, 64.2, 53.3, 49.1, 44.8, 27.0, 18.4. Analysis calc.
for C24H25N3O3: C, 71.44; H, 6.25; N, 10.41. Found: C, 71.03; H, 6.36; N, 10.10.
1.6. (1R,4S)-4-Methyl-2-p-methoxybenzyl-1-pivaloyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-
dione 2d
Mp: 161–163°C (ethyl ether). IR (KBr) ν: 1694, 1651, 1595 cm−1. 1H-NMR (CDCl3) δ: 8.25 (1H, dd,
J=8, 1.5 Hz, H-7), 7.74 (1H, ddd, J=8.2, 7.1, 1.5 Hz, H-9), 7.56 (1H, dd, J=8.2, 1.2 Hz, H-10), 7.48 (1H,
ddd, J=8.0, 7.1, 1.2 Hz, H-8), 7.13 (2H, d, J=8.7, H-20 and 60), 6.86 (2H, d, J=8.7 Hz, H-30 and 50), 5.57
(1H, s, H-1), 5.34 (1H, q, J=7.1 Hz, H-4), 5.10 (1H, d, J=14.8 Hz, Ar–CH2–N), 3.91 (1H, d, J=14.8 Hz,
Ar–CH2–N), 3.78 (3H, s, OCH3), 1.57 (3H, d, J=7.1 Hz, CH3), 1.16 (9H, s, 3(CH3)). 13C-NMR (CDCl3)
δ: 208.8, 169.4, 160.1, 159.7, 146.8, 146.5, 134.9, 130.4, 127.7, 127.1, 127.0, 126.5, 120.8, 114.5, 64.2,
55.4, 53.6, 48.7, 45.0, 27.3, 18.6. Analysis calc. for C25H27N3O4: C, 69.27; H, 6.28; N, 9.69. Found: C,
69.06; H, 6.19; N, 9.62.
1.7. (1R,4S)-1-Benzoyl-2-benzyl-4-methyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-dione 2e
1
IR (NaCl) ν: 1696, 1682, 1663 cm−1. H-NMR (CDCl3) δ: 8.23 (2H, m, H-200 and 600), 8.21 (1H,
dd, J=8.0, 1.5 Hz, H-7), 7.67 (1H, ‘t’d, J=8.0, 1.5 Hz, H-9), 7.61 (1H, d, J=8.0 Hz, H-10), 7.45 (4H, m,
H-300, 400, 500 and H-8), 7.26 (3H, m, ArH), 7.15 (2H, m, ArH), 6.07 (1H, s, H-1), 5.42 (1H, q, J=7.0 Hz,
H-4), 5.35 (1H, d, J=14.8 Hz, N–CH2–Ar), 3.90 (1H, d, J=14.8 Hz, N–CH2–Ar), 1.81 (3H, d, J=7.0 Hz,
CH3). 13C-NMR (CDCl3) δ: 192.6, 169.1, 160.3, 146.9, 145.6, 134.6, 134.5, 134.4, 133.8, 130.3, 129,
128.9, 128.5, 128.3, 127.4, 126.9, 126.7, 120.4, 63.8, 53.2, 48.8, 18.7. MS (70 eV), m/z (%)=424 (1),
423 (M+, 2), 335 (1), 334 (5), 333 (19), 320 (9), 319 (41), 318 (12), 305 (7), 304 (4), 262 (4), 229 (5),
228 (26), 215 (3), 214 (12), 200 (10), 186 (23), 185 (23), 160 (24), 146 (11), 132 (15), 117 (11), 106 (19),
105 (40), 102 (12), 92 (16), 91 (100), 92 (12), 77 (28), 76 (12), 65 (23). Analysis calc. for C26H21N3O3:
C, 73.74; H, 5.00; N, 9.92. Found: C, 73.15; H, 5.12; N, 9.55.
1.8. (1R,4S)-1-Benzoyl-2-p-methoxybenzyl-4-methyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-
dione 2f
IR (NaCl) ν: 1690, 1600 cm−1. 1H-NMR (CDCl3) δ: 8.20 (2H, m, H-200 and 600), 8.20 (1H, dd, J=8,
1.4 Hz, H-7), 7.65 (1H, d‘t’, J=8.0, 1.5 Hz, H-9), 7.58 (1H, d, J=8.0 Hz, H-10), 7.45 (1H, d, J=8.0 Hz,
H-8), 7.45 (3H, m, H-300, 400 and 500), 7.07 (2H, d, J=8.7 Hz, H-20 and 60), 6.74 (2H, d, J=8.7 Hz, H-30
and 50), 6.07 (1H, s, H-1), 5.40 (1H, q, J=7.0 Hz, H-4), 5.18 (1H, d, J=14.6 Hz, Ar–CH2–N), 3.98 (1H,
d, J=14.6 Hz, Ar–CH2–N), 3.72 (3H, s, OCH3), 1.82 (3H, d, J=7.0 Hz, CH3). 13C-NMR (CDCl3) δ: