51 g Nε-tert.butyloxycarbonyl-L-lysine were converted in a conventional manner into the benzyltriethylammonium salt and then stirred in 700 ml dimethylformamide with 81 g benzyloxycarbonyl-L-asparagine-4-nitrophenyl ester with the addition of 1 equivalent of pyridine for 48 hours at 20°. The residue left after vacuum evaporation was treated with ethyl acetate and potassium hydrogen sulfate solutions simultaneously; the thick precipitate formed was filtered off and then recrystallised from ethanol/petroleum ether. F = 174° - 175° (Z);[α]D20 = + 13.8° (c = 1.0; in pyridine). Yield = 70 g (71 % of the theoretical amount).
