6-amino-2-propylhexanoic acid

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 734 milligrams (mg) [2 millimol (mmol)] of 7-β-galactosylcoumarin-3-carboxylic acid and 210 mg (2 mmol) of N-hydroxysuccinimide in 20 ml of dimethylformamide was cooled to -10° C. while stirring under an inert atmosphere. To this was added 412 mg (2 mmol) of dicyclohexyl carbodiimide. After 15 minutes at -10° C., a clear solution was obtained. The reaction was allowed to warm to room temperature and stirred for 2 hours. It was again cooled to -10° C. and the precipitate of dicyclohexyl urea removed by filtration under vacuum. The filtrate, now containing the activated ester (3), was placed in a dropping funnel and added dropwise over a 15 minute period to a 0° C. solution consisting of 346 mg (2 mmol) of 6-amino-2-n-propylhexanoic acid (2), n=4, and 0.5 ml of triethylamine in 20 ml of water. After 1 hour at 0° C., the reaction was allowed to warm to room temperature and stirred for 2 hours. Ten grams of silicic acid was added and the solvent removed on the rotary evaporator under high vacuum. The impregnated silicic acid was placed atop a column of 120 g of silicic acid packed in 3:2 (v:v) ethyl acetate:ethanol. The column was eluted with this solvent and 15 ml fractions were collected. Fractions 28 to 40 were combined, evaporated, and the residue recrystallized from ethanol to give 365 mg (35% yield) of the labeled conjugate (4), n=4, as cream colored crystals, mp 162° C. a clear solution was obtained stirred for 2 hours It was again cooled to -10° C. the precipitate of dicyclohexyl urea removed by filtration under vacuum The filtrate, now containing the activated ester (3) was placed in a dropping funnel added dropwise over a 15 minute period to a 0° C. solution After 1 hour at 0° C. to warm to room temperature stirred for 2 hours the solvent removed on the rotary evaporator under high vacuum The column was eluted with this solvent and 15 ml fractions were collected evaporated the residue recrystallized from ethanol