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Helvetica Chimica Acta – Vol. 90 (2007)
layer was separated, washed with H2O (30 ml) and brine (30 ml), dried (MgSO4), and evaporated. FC
(cyclohexane/AcOEt 3 :1 ! 0 :1) gave a mixture of 29 and 27. Elution with CH2Cl2/MeOH (20 :1) gave
28 (28 mg, 41%). Chromatography of the mixture 29/27 on neutral Al2O3 (activity IV, AcOEt/MeOH
100 :3) afforded 29 (27 mg, 37%), each as a white powder.
Data of (Æ)-28: M.p. 181 – 1838 (dec.). Rf (CH2Cl2/MeOH 20 :1) 0.35. UV: 199 (4.21), 230 (4.54), 332
(3.91). IR (ATR): 3338w, 3204w, 3125w, 2975w, 2916w, 2861w, 1679m, 1636s, 1585s, 1487m, 1403m, 1364s,
1303m, 1272m, 1231m, 1169w, 1138w, 1101w, 1021w, 923w, 792m, 728w. 1H-NMR (300 MHz, (D6)DMSO,
353 K): 10.28 (s, HꢀN(10)); 5.79 (s, H2NꢀC(2)); 5.68 (br. s), 5.35 (d, J ¼ 0.9) (CH2¼C); 4.22 (s, 2
HꢀC(7)); 2.45, 1.97 (2d, J ¼ 15, 2 HꢀC(2’)); 2.15 (s, Me); 1.79 – 1.70 (m, CH2CH2); 1.56, 1.53 (2s,
MeꢀC(3’), MeꢀC(4’)). 13C-NMR (75 MHz, (D6)DMSO): 175.02 (s, C(9)); 161.51 (s, C(2)); 160.33 (s,
C(3a)); 154.72 (s, C(5)); 144.30 (s, C(10a)); 133.28 (s, C¼CH2); 123.61, 122.20 (2s, C(3’), C(4’)); 121.57 (t,
CH2¼C); 110.13 (s, C(10b)); 46.97 (t, C(7)); 46.14 (s, C(8)); 36.10 (t, C(2’)); 27.71, 26.41 (2t, C(5’), C(6’));
21.69 (q, Me); 18.83, 18.06 (2q, MeꢀC(3’), MeꢀC(4’)); assignment based on a HSQC and a HMBC
spectrum. HR-MALDI-MS: 339.1926 (100, [M þ H]þ, C18H23N6Oþ; calc. 339.1928), 361.1749 (4, [M þ
Na]þ, C18H22N6NaOþ; calc. 361.1747). Anal. calc. for C18H22N6O (338.41): C 63.89, H 6.55, N 24.83;
found: C 63.73, H 6.75, N 24.09.
Data of (Æ)-29. M.p. 213 – 2158 (dec.). Rf (CH2Cl2/MeOH 20 :1) 0.45. UV: 202 (4.36), 233 (4.52), 337
(3.87). IR (ATR): 3323w, 3204w, 3119w, 2961m, 2925m, 2860m, 1726w, 1674m, 1635s, 1584s, 1507m,
1468m, 1445m, 1403s, 1366s, 1350s, 1324m, 1305m, 1274s, 1221s, 1135m, 1071w, 1043w, 1011w, 919w, 848w.
1H-NMR (300 MHz, (D6)DMSO): 10.64 (br. s, HꢀN(10)); 6.50 (br. t, J ꢁ 5.7, HNꢀC(2)); 5.70, 5.33 (2 br.
s, CH2¼C); 4.22 (s, 2 HꢀC(7)); 3.28 (quint., J ꢁ 7.0, CH2Me); 2.13 (s, MeC¼CH2); 2.00 – 1.40 (m, 6
HꢀC(2’,5’,6’)); 1.54 (br. s, MeꢀC(3’), MeꢀC(4’)); 1.12 (t, J ¼ 7.2, MeCH2). 13C-NMR (75 MHz,
(D6)DMSO): 175.09 (s, C(9)); 161.46 (s, C(2)); 159.53 (s, C(3a)); 154.63 (s, C(5)); 144.27 (s, C(10a));
133.36 (s, C¼CH2); 123.59, 122.25 (2s, C(3’), C(4’)); 121.64 (t, CH2¼C); 108.61 (s, C(10b)); 47.00 (t,
C(7)); 46.22 (s, C(8)); 35.54 (t, C(2’)); 28.18 (t, MeCH2); 27.79, 26.53 (2t, C(5’), C(6’)); 21.78 (q,
MeC¼CH2); 18.95, 18.17 (2q, MeꢀC(3’), MeꢀC(4’)); 14.81 (q, MeCH2). HR-MALDI-MS: 367.2247
(100, [M þ H]þ, C20H27N6Oþ; calc. 367.2246), 389.2085 (4, [M þ Na]þ, C20H26N6NaOþ; calc. 389.2066).
(1RS,2RS,4RS) (i.e., endo)- and (1RS,2SR,4RS) (i.e., exo)-N-{2’-Amino-8’,9’-dihydro-8’-oxospiro-
[bicyclo[2.2.1]hept-5-ene-2,7’-pyrimido[4,5-b][1,4]diazepin]-4’-yl}-2-methylprop-2-enamide (endo-30
and exo-30, resp.). A mixture of 26 (50 mg, 0.17 mmol) and cyclopenta-1,3-diene (0.12 ml, 1.36 mmol)
in toluene (6 ml) in a sealed V-vial was put into an oil-bath of 1108 and stirred for 0.5 h. The resulting
suspension was evaporated, and FC (CH2Cl2/AcOEt 2 :1) gave endo-30/exo-30 7:3 (48 mg, 84%). White
powder. M.p. > 1228 (dec.). Rf (CH2Cl2/AcOEt 1:1) 0.15. UV: 229 (4.41), 328 (4.02). IR (ATR): 3555w,
3369w, 3306w, 3198w, 3083w, 2973w, 2847w, 1737m, 1704m, 1665m, 1627s, 1616s, 1549s, 1465s, 1450s, 1382s,
1334m, 1310s, 1229m, 1173s, 1118m, 1076w, 1044m, 1026m, 951w, 937w, 870m, 818m. 1H-NMR (300 MHz,
CD2Cl2; endo/exo 7:3): 11.87 (s, 0.3 H), 11.84 (br. s, 0.7 H) (HNꢀC(8’)); 9.38 (br. s, 0.7 H), 9.28 (s, 0.3 H)
(HNꢀC(4’)); 7.35 (s, 0.7 H), 7.13 (s, 0.3 H) (HꢀC(6’)); 6.34 – 6.31 (m, 0.6 H), 6.25 (br. s, 1.4 H)
(HꢀC(5), HꢀC(6)); 6.25 (br. s, NH2); 5.83 (br. s, 0.7 H), 5.79 (br. s, 0.3 H) (CHH’¼); 5.54 (q, J ¼ 1.2,
0.7 H), 5.52 (q, J ¼ 1.2, 0.3 H) (CHH’¼); 3.51 (s, 0.3 H), 3.28 (br. s, 0.7 H) (HꢀC(1)); 2.90 (s, 0.3 H), 2.84
(br. s, 0.7 H) (HꢀC(4)); 2.01 (s, 2.1 H), 1.99 (s, 0.9 H) (Me); 1.69 – 1.42 (m, 2.8 H), 1.28 – 1.12 (m, 1.2 H)
(2 HꢀC(3), 2 HꢀC(7)). 1H-NMR (300 MHz, (D6)DMSO; endo/exo 7:3): 10.71 (s, 0.3 H), 10.62 (s,
0.7 H) (HNꢀC(8’)); 9.88 (s, 0.7 H), 9.74 (s, 0.3 H) (HNꢀC(4’)); 7.33 (br. s, 0.7 H), 7.12 (s, 0.3 H)
(HꢀC(6’)); 6.61 (br. s, NH2); 6.38 – 6.12 (m, HꢀC(5), HꢀC(6)); 5.85 (s, 0.7 H), 5.77 (s, 0.3 H)
(CHH’¼); 5.56 (s, 0.7 H), 5.51 (s, 0.3 H) (CHH’¼); 3.37 – 3.27 (m, HꢀC(1)); 2.82 – 2.73 (m, HꢀC(4));
1.89 (s, 2.1 H), 1.86 (s, 0.9 H) (Me); 1.64 – 1.30 (m, 2 HꢀC(3), 2 HꢀC(7)). 13C-NMR (75 MHz, CD2Cl2;
endo/exo 7:3): 170.95, 169.00 (2s, C(8’)); 165.50, 165.42 (2s, C¼O); 161.53, 161.48 (2s, C(4’)); 159.51,
159.07 (2d, C(6’)); 155.99, 155.96 (2s, C(2’)); 148.24, 147.73 (2s, C(9’a)); 141.78, 137.63 (2d, C(6)); 136.29,
133.37 (2d, C(5)); 140.74 (s, C¼CH2); 121.91 (t, CH2¼); 111.88, 111.34 (2s, C(4’a)); 61.38, 60.87 (2s,
C(2)); 48.76, 48.10 (2t, C(7)); 47.62, 46.50 (2d, C(1)); 42.74, 41.34 (2d, C(4)); 40.54, 38.86 (2t, C(3)); 18.28
(q, Me). HR-MALDI-MS: 339.1558 (34, [M þ H]þ, C17H19N6O2þ ; calc. 339.1564), 361.1383 (4, [M þ
Na]þ, C11H18N6NaO2þ ; calc. 361.1383). Signals of the ene product (retro-Diels – Alder product):
273.1084 (100, [M þ H]þ, C12H13N6O2þ ; calc. 273.1095), 295.0914 (5, [M þ Na]þ, C12H12N6NaOþ2 ; calc.
295.0914).