Table 6. SAR of C32 Modifications and Active-Site Inhibitors.

| entry | compound no. | PEG repeats | R | active-site inhibitor (R1) | pS6K IC50 (nM) | p4EBP1 IC50 (nM) | pAKT IC50 (nM) | selectivity |
|---|---|---|---|---|---|---|---|---|
| 1 | 35 | 8 | OMe | MLN | 0.24 | 1.3 | 13 | 10.0 |
| 2 | 36 | 8 | OH | 0.49 | 1.4 | 8.4 | 6.0 | |
| 3 | 37 | 8 | OMe | “rigid MLN” | 0.17 | 1.6 | 35 | 21.9 |
| 4 | 38 (RMC-5552) | 8 | OH | 0.14 | 0.48 | 19 | 39.6 | |
| 5 | 39 | 8 | OMe | XL388 | 0.19 | 0.97 | 35 | 36.1 |
| 6 | 40 (RMC-6272) | 8 | OH | 0.14 | 0.44 | 12 | 27.3 |