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

Participants

Reaction Steps

900 mg of Z-Sta-OH (for manufacture see stage 1.12), 1.24 g of H-Ile-His-Lys(Boc)-OMe and 560 mg of HOBt×H2O are dissolved in 13 ml of DMF. After the addition of 600 mg of DCCI, the whole is left to stand at room temperature for 20 hours, then the DCH which has crystallised out is filtered off and the filtrate is concentrated to dryness. The greasy residue is triturated at 0° with 30 ml of diisopropyl ether, the solvent is decanted and the residue is dried. Purification is carried out by Craig partitioning in the system methanol/buffer/ethylene chloride/chloroform (10:3:8:4; buffer=14.3 ml of glacial acetic acid and 9.6 g of ammonium acetate in 1000 ml of H2O) over 700 stages. The thin layer chromatographically pure fractions (K=0.5) are combined, strongly concentrated and lyophilised. To remove acetic acid, the product is dissolved and reprecipitated from 5% strength methanolic NaHCO3 solution, yielding Z-Sta-Ile-His-Lys(Boc)-OMe in the form of amorphous powder; Rf (B)=0.8; Rf (I)=0.56.

Provenance & Evidence