Potassium Hydroxide → HCID 131721919, compound

Participants

Reaction Conditions

Reaction Steps

Boc-Gly-Pro-Nleu-OEt (4.3 g, 0.0104 mol.) was dissolved in 80 ml THF/H2) (v/v, 1:1) and the solution was chilled to 0° C. on a water-ice bath. KOH (1.1 g dissolved in 20 ml H2O) was added while stirring the solution. After a while, the bath was removed and the stirring was continued for one more hour. The THF was removed under reduced pressure. The aqueous solution was extracted by ethyl acetate 2×50 ml. Then, the aqueous layer was chilled to 0° C. and was acidified to about pH=3 by addition of concentrated HCl while swirling the solution vigorously at the same time (the aqueous layer was covered by 50 ml ethyl acetate). The product was extracted from the aqueous layer by ethyl acetate 3×50 ml. The organic layer was combined and dried by Na2SO4. The ethyl acetate was removed under reduced pressure. Column chromatography (E/H:5:2) was carried out to obtain the pure product (white solid, 3.6 g, 92%). TLC Rf=0.44 (developing solvents: CMA, 85:15:3). FAB-MS, observed (M+H)+=386. Analytical RP-HPLC chromatogram, single peak, retention time RT=13 min. (25-60% B in 30 min.). 1H-NMR (500 MHz, DMSO-d6, 25° C., assignment by TOCSY) δ12.50 (s, 1H, carboxyl), 6.62 (m, 1H, Gly-NH), 4.92 (d, Pro-α), 4.72 (d, Pro-α), 4.56 (d, Nleu-α), 4.48 (d, Pro-α), 4.12 (m, Nleu-α), 4.00-3.90 (m, Nleu-α), 3.83-3.66 (m, Nleu-α, Gly-α), 3.64-3.50 (m, Gly-α, Nleu-α), 3.50-3.33 (m, Pro-δ), 2.34-1.60 (sets of bands, Pro-β, Pro-γ, Nleu-γ), 1.38 (s, 9H, Boc-CH3), 0.88 (dd, Nleu-δ), 0.75 (dd, Nleu-δ).

Provenance & Evidence