Nitrogen → N-hydroxysuccinimide trifluoroacetate

Participants

Reaction Steps

N-hydroxysuccinimide trifluoroacetate was prepared by stirring N-hydroxysuccinimide (NHS) and 4 eq trifluoroacetic anhydride for 5 h. The mixture was concentrated under reduced pressure and further dried under high vacuum overnight. The product was obtained as a white, highly hygroscopic solid and stored in an anhydrous desiccator before use. The obtained approximately 1.1 g 2,2′-(hex-5-ynylazanediyl)diacetic acid was activated by 2.4 eq N-hydroxysuccinicimide trifluoroacetate in 10 mL anhydrous DMF under a stream of dry N2. The mixture was stirred overnight and monitored by TLC using hexanes:ethyl acetate (=2:1) as the mobile phase. After completion of the reaction, the mixture was concentrated to approximately 500 μL by rotary evaporation and subjected to flash chromatography using hexanes:ethyl acetate (=2:1) as the mobile phase. The final product, NHS-activated 2,2′-(hex-5-ynylazanediyl)diacetic acid (CXL-1) was concentrated by rotary evaporation, and obtained as a pale yellow oil. Several 200 μL aliquots of 50 mM stock solution dissolved in anhydrous dimethyl sulfoxide (DMSO) were prepared and stored at −80° C. The sealed stock aliquots were opened immediately before use, and NHS activation was verified by ESI-MS in 100% ACN. ESI-MS [M+H]+ m/z 408.1, [M+Na]+ m/z 420.0. This reaction yield can be improved by adding stoichiometric equivalents of triethylamine.

Provenance & Evidence