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4.1.12.5. Phenyl [4-(benzyl olean[3,2-b]pyrazine-12-en-28-oate-23-oxy)-4-oxo]-4-[(2-nitroxy)ethyl] butyrate (21). Yield: 81%
(after chromatograph with chloroform/methanol, 500:1) as a white solid. mp 220-223 ; Rf = 0.62 (chloroform/methanol
1
150:1 v/v); [α]20D = 14.44 (c = 0.18, CH3OH/CHCl3 3:2 v/v); H NMR (400 MHz, CDCl3) δ 0.60 (3H, s, -CH3), 0.80 (3H, s,
-CH3), 0.83 (3H, s, -CH3), 0.86 (3H, s, -CH3), 1.00 (3H, s, -CH3), 1.20 (3H, s, -CH3), 2.40-2.43 (2H, m, H-2), 2.53-2.58 (1H, m,
H-1A), 2.59-2.62 (2H, m, -COCH2-), 2.90-2.93 (1H, m, H-1B), 2.92-2.95 (1H, m, H-18), 2.94-2.98 (2H, m, -COCH2-),
4.25-2.67 (2H, m, H-23), 4.55 (2H, t, J = 2.3 Hz, -OCH2-), 5.00 (1H, d, J = 12.57 Hz, CH2Ar), 5.05 (1H, d, J = 12.54 Hz,
CH2Ar), 5.29 (1H, t, H-12), 7.05 (2H, d, J = 8.49 Hz, H-Ar), 7.21 (2H, d, J = 8.49 Hz, H-Ar), 7.31-7.37 (5H, m, H-Ar), 8.35,
8.38 (each 1 H, ds, J = 2.3 Hz, H-pyrazinem); 13C NMR (100 MHz, CDCl3) δ 15.76, 16.61, 19.83, 23.05, 23.31, 23.61, 25.67,
26.23, 27.56, 27.67, 28.43, 28.96, 29.09, 29.68, 30.71, 31.75, 32.32, 32.72, 33.13, 33.87, 36.55, 39.15, 41.49, 41.84, 43.23,
45.62, 45.84, 46.07, 46.77, 47.48, 65.97, 68.45, 68.99, 70,24, 71.03, 76.68, 76.99, 77.20, 77.31, 121.86, 122.22, 127.95,
128.02, 128.44, 129.84, 136.38, 142.53, 143.69, 149.63, 152.09, 171.42. ESI-HRMS m/z calcd. for C51H63N3O9 [M + H]+:
862.4564, found: 862.4645.
4.1.12.6. Phenethyl [4-(benzyl olean[3,2-b]pyrazine-12-en-28-oate-23-oxy)-4-oxo]-4-[O-(2-nitro)ethyl] butyrate (22). Yield: 75%
(after chromatograph with chloroform/methanol, 500:1) as a white solid. mp 223-227 ; Rf = 0.52 (chloroform/methanol 150:1
v/v); [α]20D = 11.69 (c = 0.16, CH3OH/CHCl3 3:2 v/v); 1H NMR (400 MHz, CDCl3) δ 0.70 (3H, s, -CH3), 0.89 (3H, s, -CH3), 0.92
(3H, s, -CH3), 0.95 (3H, s, -CH3), 1.19 (3H, s, -CH3), 1.29 (3H, s, -CH3), 2.39-2.42 (2H, m, H-2), 2.54-2.58 (1H, m, H-1A), 2.85
(2H, t, J = 7.08 Hz, -COCH2-), 2.92-2.95 (1H, m, H-1B), 2.95-2.99 (1H, m, H-18), 4.17-4.20 (2H, m, H-23), 4.24-4.33 (4H, m,
-OCH2-), 4.80-4.84 (2H, m, -OCH2-), 5.09 (1H, d, J = 12.57 Hz, CH2Ar), 5.10 (1H, d, J = 12.54 Hz, CH2Ar), 5.39 (1H, t, H-12),
6.86 (2H, d, J = 8.52 Hz, H-Ar), 7.28 (2H, d, J = 8.52 Hz, H-Ar), 7.33-7.37 (5H, m, H-Ar), 8.31, 8.44 (each 1 H, ds, J = 2.3 Hz,
H-pyrazinem); 13C NMR (100 MHz, CDCl3) δ 15.75, 16.63, 19.82, 23.08, 23.34, 23.60, 25.76, 27.61, 28.86, 28.93, 29.20, 29.78,
30.71, 31.81, 32.34, 33.09, 33.88, 34.13, 36.57, 38.66, 39.18, 41.53, 41.89, 43.22, 45.64, 45.82, 46.06, 46.80, 47.20, 47.66, 47.53,
64.07, 65.28, 65.97, 69.36, 71.02, 76.24, 76.88, 77.20, 77.46, 114.64, 122.27, 127.95, 128.02, 128.44, 130.01, 136.38, 142.46,
143.70, 152.22, 156.4, 171.87, 177.20. ESI-HRMS m/z calcd. for C53H67N3O10 [M + H]+: 906.4826, found: 906.4904.
4.1.12.7. Phenyl [2-(benzyl olean[3,2-b]pyrazine-12-en-28-oate-23-oxy)-oxo]-4-[(2-nitroxy)ethyl] benzoate (23). Yield: 73%
(after chromatograph with chloroform/methanol, 500:1) as a white solid. mp 196-200 ; Rf = 0.60 (chloroform/methanol 80:1
v/v); [α]20D = 1.25 (c = 0.08, CH3OH/CHCl3 3:2 v/v); 1H NMR (400 MHz, CDCl3) δ 0.70 (3H, s, -CH3), 0.89 (3H, s, -CH3), 0.92
(3H, s, -CH3), 0.95 (3H, s, -CH3), 1.19 (3H, s, -CH3), 1.29 (3H, s, -CH3), 2.39-2.42 (2H, m, H-2), 2.54-2.58 (1H, m, H-1A), 2.85
(2H, t, J = 7.08 Hz, -COCH2-), 2.92-2.95 (1H, m, H-1B), 2.95-2.99 (1H, m, H-18), 4.17-4.20 (2H, m, H-23), 4.24-4.33 (4H, m,
-OCH2-), 4.80-4.84 (2H, m, -OCH2-), 5.09 (1H, d, J = 12.57 Hz, CH2Ar), 5.10 (1H, d, J = 12.54 Hz, CH2Ar), 5.39 (1H, t, H-12),
6.86 (2H, d, J = 8.52 Hz, H-Ar), 7.28 (2H, d, J = 8.52 Hz, H-Ar), 7.33-7.37 (5H, m, H-Ar), 8.31, 8.44 (each 1 H, ds, J = 2.3 Hz,
H-pyrazinem); 13C NMR (100 MHz, CDCl3) δ 15.67, 16.57, 19.77, 19.83, 23.00, 23.27, 23.56, 25.59, 27.50, 29.67, 29.88, 30.67,
31.73, 32.26, 32.73, 33.06, 33.56, 33.81, 36.55, 39.09, 41.47, 41.81, 41.99, 43.41, 45.61, 45.81, 46.12, 46.73, 47.62, 65.92, 71.77,
76.24, 76.88, 77.20, 77.46, 121.87, 122.14, 127.91, 127.98, 128.40, 128.50, 128.94, 129.90, 130.01, 131.14, 131.20, 132.18,
133.80, 136.34, 141.66, 142.50, 143.68, 149.87, 152.16, 156.08. ESI-HRMS m/z calcd. for C55H63N3O9 [M + H]+: 910.4578,