Dicyclohexylcarbodiimide → Z-Sta-Sar-His-Lys(Boc)-OMe

Participants

Reaction Steps

254 mg of Z-Sta-OH (see stage 1.12), 297 mg of H-Sar-His-Lys(Boc)-OMe, 97 mg of HOBt×H2O and 196 mg of DCCI are dissolved, in this sequence, in 3 ml of DMF and the whole is left to stand for 20 hours at room temperature. The DCH which has crystallised out is filtered off, the filtrate is concentrated to dryness, heated for 1 hour at 60° in 7 ml of methanol/glacial acetic acid/H2O (94:3:3), and this solution is again concentrated to dryness. The oily residue is purified by chromatography over 75 g of silica gel (Merck No. 60, 230-400 mesh) by elution with CHCl3 /MeOH (9:1). The pure fractions are dissolved in ethyl acetate, washed with NaHCO3 solution and with H2O and, by concentration of the organic phase, Z-Sta-Sar-His-Lys(Boc)-OMe is obtained in amorphous form (honey); Rf (F)=0.15; Rf (I)=0.5.

Provenance & Evidence