Diisopropylcarbodiimide → Ninhydrin

Participants

Reaction Conditions

Reaction Steps

2.7 g of the aminomethylated film was pre-washed in 70 ml of DMF/CH2Cl2 (1:2 v/v) for 3×3 min in a 100 ml reaction vessel on a manual SPPS shaker. 2.49 g (7 mmol) of Boc-protected 3-(4-benzhydrylamine)propionic acid and 1.07 g (7 mmol) of HOBt were dissolved in 50 ml of DMF/CH2Cl2 (1:1 v/v), and the solution was stirred in a screw-capped tube for 3 min at 0° C. A solution of 1.1 ml of DIC in 20 ml of CH2Cl2 was added, and the mixture was then stirred for 25 min at 0° C. and added to the pre-washed aminomethylated film. After shaking the resulting "mixture" for 3 hours, the film was isolated by filtration, washed with CH2Cl2, neutralized with DIEA/CH2Cl2 (5:95 v/v), washed with CH2Cl2 and dried in vacuo. Quantitative Kaiser ninhydrin tests (vide supra) indicated that ca. 0.08 mmol of the initial 0.37 mmol of amino groups per gram of film had not coupled to the Boc-protected BHA reagent. These remaining free amino groups were acetylated ("capped") using acetic anhydride/pyridine/CH2Cl2 (1:1:2 v/v/v), leaving only 0.006 mmol of uncapped, free amino groups per gram (as determined by quantitative Kaiser ninhydrin testing).

Provenance & Evidence