N,N'-Dicyclohexylurea → Z-Ser(tBu)-Asn-Leu-OMe

Participants

Reaction Steps

A solution of 8.90 g of H-Asn-Leu-OMe and 11.0 g of Z-Ser(tBu)-OH in 100 ml of freshly distilled dimethylformamide is cooled to 0° C. and mixed with 3.90 g of N-hydroxysuccinimide and 8.70 g of dicyclohexyl carbodiimide. After allowing the batch to stand for 30 minutes at 0° C. and then for 18 hours at 25° C. the precipitated dicyclohexylurea is suctioned off and the filtrate poured into 800 ml of ice water. The resulting crystalline precipitate is dried under vacuum at 40° C. and then recrystallized from aqueous methanol. The resulting analytically pure product - Z-Ser(tBu)-Asn-Leu-OMe -melts at 202°-205° C. Optical rotation [α]D20 =18° (c=1.05 in glacial acetic acid).

Provenance & Evidence