Sodium Hydroxide → Boc-Pro-His-OH

Participants

Reaction Steps

1.25 g of Boc-Pro-OSu [G. W. Anderson et al., J. Amer. Chem. Soc. 86, 1839 (1964)] and 0.68 g of H-His-OH are suspended in 4 ml of H2O and 2 ml of dioxan. While stirring vigorously, 2N NaOH is added by means of a pH stat at a pH value of 9.0. After 45 minutes the absorption of NaOH ceases. The now clear solution is stirred for a further 10 minutes, the pH value is adjusted subsequently to 5.0 with 4N HCl, and the whole is concentrated to approximately 5 ml. After the addition of 20 ml of H2O, the whole is again concentrated to approximately 5 ml and then purified by chromatography over a column of absorber resin, diaion HP-20 (φ=1.6 cm; length=20 cm). The bulk of this product is eluted with 20% isopropanol in H2O. The fractions that are pure according to thin layer chromatography are combined, concentrated almost to dryness and, after the addition of H2O, lyophilised, yielding Boc-Pro-His-OH in the form of an amorphous powder; Rf (E)=0.45; Rf (A)=0.21.

Provenance & Evidence