3.2 Experimental Procedures
51
(C
2 ), 16.7 (C
25 ). [α]
20
D +39.0 (c 1.0, CDCl 3 ). HRMS (ESI-TOF) m/z:
[M + Na]
+ Calcd for C 31 H 48 ClNNaO 3
+ 540.3215; Found 540.3212.
3.2.8 23-Acetoxy-3-(acetoxyimino)-12α-chloro-olean28,13β-olide (7a)
N
H
H
H
Cl
O
O
O
O
O
O
1
2
3
4
5
6
7
8
9
10
11
12 13
14
15
16
17
18
19
20
21
22
28
24
23
25
26
29
27
30
31
32
33
34
A screw cap vial, equipped with magnetic stirring bar, was charged with a suspension of 6a (100 μmol, 50.4 mg, 1 equiv) in a mixture of Ac 2 O (2.65 mmol,
250 μl, 26.5 equiv) and AcOH (250 μl). The mixture was left stirring at
20 °C for 5 h. Pd(OAc) 2 (12.5 μmol, 2.8 mg, 0.125 equiv) and PhI(OAc) 2
(150 μmol, 48.3 mg, 1.5 equiv) were added subsequently and the reaction
was left stirring at 20 °C for 48 h. Solvents were removed under reduced
pressure at 50 °C. Purification by column chromatography (silica gel, heptane/EtOAc = 4:1) gave the target compound as colourless solid (34.4 μmol,
20.8 mg, 34 %; dr 80:20).
1
H-NMR (600 MHz, CDCl 3 , major isomer): δ 4.22 (d, J = 11.0 Hz,
1 H, H
23a ), 4.21–4.16 (m, 1 H, H
12 ), 4.10 (d, J = 11.0 Hz, 1 H, H
23b ),
2.74–2.63 (m, 1 H, H
2a ), 2.34–2.25 (m, 2 H, H
2b,11a ), 2.21–2.12 (m, 5 H,
H
16a,19a,32 ), 2.07 (s, 3 H, H
34 ), 2.05–2.00 (m, 2 H, H
18,19b ), 1.94 (td, J =
13.8, 6.1 Hz, 1 H, H
15a ), 1.84–1.77 (m, 2 H, H
1a,9 ), 1.76–1.70 (m, 1 H, H
11b ),
1.68–1.62 (m, 2 H, H
22ab ), 1.57–1.48 (m, 3 H, H
5,6a,7a ), 1.47–1.41 (m, 1 H,
H
6b ), 1.39 (s, 3 H, H
27 ), 1.36–1.26 (m, 5 H, H
1b,7b,16b,21ab ), 1.26–1.21 (m,
4 H, H
15b,26 ), 1.19 (s, 3 H, H
24 ), 0.99 (s, 3 H, H
29 ), 0.94 (s, 3 H, H
25 ), 0.91
(s, 3 H, H
30 ).
13 C-NMR (150 MHz, CDCl 3 , major isomer): δ 179.0
(C
28 ), 171.1 (C
33 ), 170.4 (C
31 ), 169.7 (C
3 ), 91.6 (C
13 ), 68.4 (C
23 ), 65.0
51
(C
2 ), 16.7 (C
25 ). [α]
20
D +39.0 (c 1.0, CDCl 3 ). HRMS (ESI-TOF) m/z:
[M + Na]
+ Calcd for C 31 H 48 ClNNaO 3
+ 540.3215; Found 540.3212.
3.2.8 23-Acetoxy-3-(acetoxyimino)-12α-chloro-olean28,13β-olide (7a)
N
H
H
H
Cl
O
O
O
O
O
O
1
2
3
4
5
6
7
8
9
10
11
12 13
14
15
16
17
18
19
20
21
22
28
24
23
25
26
29
27
30
31
32
33
34
A screw cap vial, equipped with magnetic stirring bar, was charged with a suspension of 6a (100 μmol, 50.4 mg, 1 equiv) in a mixture of Ac 2 O (2.65 mmol,
250 μl, 26.5 equiv) and AcOH (250 μl). The mixture was left stirring at
20 °C for 5 h. Pd(OAc) 2 (12.5 μmol, 2.8 mg, 0.125 equiv) and PhI(OAc) 2
(150 μmol, 48.3 mg, 1.5 equiv) were added subsequently and the reaction
was left stirring at 20 °C for 48 h. Solvents were removed under reduced
pressure at 50 °C. Purification by column chromatography (silica gel, heptane/EtOAc = 4:1) gave the target compound as colourless solid (34.4 μmol,
20.8 mg, 34 %; dr 80:20).
1
H-NMR (600 MHz, CDCl 3 , major isomer): δ 4.22 (d, J = 11.0 Hz,
1 H, H
23a ), 4.21–4.16 (m, 1 H, H
12 ), 4.10 (d, J = 11.0 Hz, 1 H, H
23b ),
2.74–2.63 (m, 1 H, H
2a ), 2.34–2.25 (m, 2 H, H
2b,11a ), 2.21–2.12 (m, 5 H,
H
16a,19a,32 ), 2.07 (s, 3 H, H
34 ), 2.05–2.00 (m, 2 H, H
18,19b ), 1.94 (td, J =
13.8, 6.1 Hz, 1 H, H
15a ), 1.84–1.77 (m, 2 H, H
1a,9 ), 1.76–1.70 (m, 1 H, H
11b ),
1.68–1.62 (m, 2 H, H
22ab ), 1.57–1.48 (m, 3 H, H
5,6a,7a ), 1.47–1.41 (m, 1 H,
H
6b ), 1.39 (s, 3 H, H
27 ), 1.36–1.26 (m, 5 H, H
1b,7b,16b,21ab ), 1.26–1.21 (m,
4 H, H
15b,26 ), 1.19 (s, 3 H, H
24 ), 0.99 (s, 3 H, H
29 ), 0.94 (s, 3 H, H
25 ), 0.91
(s, 3 H, H
30 ).
13 C-NMR (150 MHz, CDCl 3 , major isomer): δ 179.0
(C
28 ), 171.1 (C
33 ), 170.4 (C
31 ), 169.7 (C
3 ), 91.6 (C
13 ), 68.4 (C
23 ), 65.0