4-Methylmorpholine → Z-Sta-Ala-OC(CH3)3

Participants

Reaction Steps

371 mg of Z-Sta-OH (cf. stage 1.12), 240 mg of H-Ala-OC(CH3)3 and 184 mg of HOBt×H2O are dissolved in 10 ml of DMF. After cooling the solution to 0°, 133 mg of N-methylmorpholine and 321 mg of DCCI are added. The whole is stirred for 1 hour at 0° and for 14 hours at 25°, then the DCH formed is filtered off and the filtrate is concentrated to dryness by evaporation. The residue is taken up in ethyl acetate and the solution is extracted with saturated sodium bicarbonate solution. The organic phases are dried, concentrated by evaporation and the residue is flash-chromatographed over 80 g of silica gel (grain size 0.04-0.063 mm) [eluant: methylene chloride/ether (4:1), fractions of approximately 25 ml]. Fractions 24-40 are combined, concentrated by evaporation, the residue is dissolved in a small amount of methylene chloride, and the solution is filtered and concentrated by evaporation once more. After drying the residue in a high vacuum, Z-Sta-Ala-OC(CH3)3 is obtained as a slightly yellowish oil; Rf (methylene chloride/diethyl ether [4:1])=0.10.

Provenance & Evidence