Compound | R1 | R2 |
18 | H |
|
19 | H |
|
20 | H |
|
21 | H |
|
22 | H |
|
23 | H |
|
24 | H |
|
25 | H |
|
26 | H |
|
27 | H |
|
28 | H |
|
29 |
| |
30 |
| |
31 |
|