Dicyclohexylcarbodiimide → Nalphat-Butoxycarbonyl-L-tryptophyl-O-benzyl-D-seryl-O-benzyl-L-tyrosyl-D-alanine

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Reaction Conditions

Reaction Steps

Nαt-Butoxycarbonyl-L-tryptophyl-O-benzyl-D-seryl-O-benzyl-L-tyrosyl-D-alanine resin is prepared from 8 g. of Nα-t-butoxycarbonyl-O-benzyl-L-tyrosyl-D-alanine resin by successive coupling, according to the general process for solid phase synthesis given in Example 1, with (13 g., 9.8 mmol, of Nα-t-butoxycarbonyl-O-benzyl-D-serine and 2 g., 9.7 mmol, of dicyclohexylcarbodiimide and (2) 3 g., 9.8 mmol, of Nα-t-butoxycarbonyl-L-tryptophan and 2 g. of dicyclohexylcarbodiimide. The resin is washed with ethanol and dried. It is then stirred for twenty-four hours at 25° C. with 200 ml. of methanol and 20 ml. of triethylamine. The mixture is filtered and the methanol solution evaporated. The residue is solidified from ether-petroleum ether; 2 g.; m.p. 155°-156° C.

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