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MeO 2C
O
O
O
N
H
N
R 1
O
N
Ph
[10c-Methyl-5-(1-methyl-3-oxo-propyl)-3,4,8,10-tetraoxo-9-phenyl-
4,6,7,7a,8,9,10,10a,10b,10c-decahydro-2-oxa-3a,9-diaza-dicyclopenta[a,h]naphthalen-1-
ylideneamino]-acetic acid methyl ester (158a). A solution of pyran 157a (11 mg, 18 µmol) in
CDCl3 was allowed to stand at rt for 24 h (slow hydrolysis to 158a was catalyzed by traces of
acid in CDCl3). The solvent was removed under vacuum to afford 158a (11mg, >95%).
Alternatively, addition of 1M HCl (50 µL) accelerates the hydrolysis to 3 h.
1 H NMR (300 MHz, CDCl3): δ 9.58 (s, 1H), 7.48-7.31 (m, 6H), 7.18-7.16 (m, 2H), 7.08-7.06 (m,
2H), 4.36 (d, J = 18.0 Hz, 1H), 4.37-4.34 (m, 1H), 4.21 (d, J = 18.1 Hz, 1H), 3.79 (s, 3H), 3.44-
3.31 (m, 7H), 2.87 (dd, J = 19.1, 6.2 Hz, 1H), 2.72 (dd, J = 19.2, 5.7 Hz, 1H), 2.60-2.46 (m, 1H),
2.28-2.13 (m, 1H), 1.25 (d, J = 6.9 Hz, 3H); 13 C NMR (75 MHz, CDCl3): δ 200.8, 176.8, 175.8,
170.1, 158.3, 153.6, 147.7, 146.0, 134.2, 132.0, 131.1, 130.0, 128.9, 128.5, 128.4, 125.8, 64.5,
52.2, 49.0, 48.9, 47.4, 41.2, 40.6, 39.8, 27.0, 26.6, 20.2, 18.5; IR (thin film): ν 2954, 2256, 1838,
1743, 1710 cm -1 .
MeO 2C
O
O
158a
O
O
N
H
N
Bn
O
N
Ph
(10c-Benzyl-5-ethyl-3,4,8,10-tetraoxo-9-phenyl-4,6,7,7a,8,9,10,10a,10b,10c-decahydro-2-
oxa-3a,9-diazadicyclopenta[a,h]naphthalen-1-ylideneamino)acetic acid methyl ester (161a).
161a
215
O
O
H