Table 1.
Reactivity of penicillins in presence of Dithiothreitol (DTT) in different conditions.
| Penicillin | pH | Penicillin : DTT ratio | Incubation time | Cyclization product (DKP) % of total |
|---|---|---|---|---|
| AXa | 5.8 | 1:2 | 14 h | 100 |
| AXb | 7.4 | 1:1.13 | 6 h | 62 |
| 30 h | 93 | |||
| AXb | 7.4 | 1.32:1 | 4 h | 43 |
| 7 h | 60 | |||
| 24 h | 99 | |||
| AXb | 7.4 | 3.46:1 | 4 h | 28 |
| 7 h | 34 | |||
| 24 h | 99 | |||
| AXa | 7.4 | 1.32:1 | 14 h | 85 |
| AXa | 7.4 | 3.46:1 | 14 h | 60 |
| BPb | 7.4 | 1:1 | 24 h | 0 |
| BPb | 11 | 1:1 | 24 h | 0 |
| AMPb | 7.4 | 1:1 | 24 h | 95 |
| AMPb | 11 | 1:1 | 24 h | 95 |
Incubations were carried out at 37°C for the time stated in each case in (a) distilled water or phosphate buffer saline (PBS) and then lyophilized; or (b) deuterated solvent (D2O, PBS or carbonate). In both cases, 1H-NMR was employed for identifying and quantifying the resulting cyclization product.