Fmoc-removal using 5, 10 and 20% piperidine in DMF with half-lives and time needed for 99.99% deprotection for resin-bound Fmoc-Gln, Fmoc-Val, Fmoc-Pro, and Fmoc-Lys(Boc)61a.
| Resin-bound amino acid | 20% piperidine in DMF | 10% piperidine in DMF | 5% piperidine in DMF | |||
|---|---|---|---|---|---|---|
| t 1/2 (s) | Deprotection ≥ 99.99%b (min) | t 1/2 (s) | Deprotection ≥ 99.99%b (min) | t 1/2 (s) | Deprotection ≥ 99.99%b (min) | |
| Fmoc-Gln | 20.5 | 4.5 | 23.2 | 5.1 | 53.1 | 11.8 |
| Fmoc-Val | 41.5 | 9.2 | 44.6 | 9.9 | 47.1 | 10.4 |
| Fmoc-Pro | 25.4 | 5.6 | 27.0 | 5.9 | 32.0 | 7.1 |
| Fmoc-Lys(Boc) | 10.3 | 2.3 | 22.3 | 4.9 | 27.4 | 6.1 |
a
The deprotection solution was added to the resin and after 10 s was filtered and the UV-absorption of the filtrate was measured. The procedure was repeated until the UV absorption of the filtrate <0.05 AU. The percentage of the Fmoc-removal was expressed as a percentage of the absorption measured when the deprotection solution was added to the same amount of resin sample for 20 min. The time needed for 50% Fmoc-removal corresponds to the half-life of the deprotection step.
b
Time needed for 99.99% deprotection = −ln 0.0001 t1/2/0.693.