Dicyclohexylcarbodiimide → Divinylbenzene-styrene

Participants

Reaction Steps

N-Hexadecylsulfonyl-(O-t-butyl)-L-aspartic acid (189 mg, 0.395 mmole), 1-hydroxybenzotriazole (55.1 mg, 0.395 mmole) and dicyclohexylcarbodiimide (82.5 mg, 0.395 mmole) in 0.50 mL DMF was stirred at room temperature for 45 minutes. A 0.050 mL aliquot of this solution was added to the tetrabutylammonium salt of 6 (25 mg) in 0.20 mL of DMF and stirred at room temperature for 60 minutes. The reaction mixture was quenched by dilution with 8 mL of 25% acetonitrile (AcN) 0.12 M in ammonium phosphate (pH 7.2), aged at room temperature, then filtered through a membrane (Whatman GD/X). The product was isolated from the filtrate by low resolution reverse phase chromatography on a 5 g styrene-divinylbenzene resin cartridge (25×45 mm, Supelco EnviChrom-P). The sample-loaded cartridge was eluted with stepwise increasing concentrations of AcN in sodium phosphate (aqueous pH 6.9); product was eluted with 57% AcN 0.010 M in pH 6.9 buffer. Product-containing fractions were pooled, diluted with an equal volume of distilled water and then desalted on the same 5g resin cartridge which had been rinsed with 75% and 25% AcN. The diluted fraction pool was applied to the cartridge, which was rinsed with 16 mL 25% AcN 0.125 M in ammonium phosphate (pH 7.2), then 24 mL salt-free 25% AcN. The product was stripped from the cartridge with 48 mL 67% AcN. AcN was removed under vacuum from the strip fraction and the aqueous solution was freeze dried to give the desired product. Yield: 4.7 mg of a white solid, 69% by HPLC (215 nm area %); C62H104N12O20S; FABMS m/z 1392 (M+Na)+. (calc. for C62H104N12O20S+Na, 1391.7).

Provenance & Evidence