1-Hydroxybenzotriazole → 2-{(1R,3R)-1-[(2S,3S)-2-tert-Butoxycarbonylamino-3-methyl-pentanoyloxy]-4-methyl-3-methylamino-pentyl}-thiazole-4-carboxylic acid ethyl ester

Participants

Reaction Steps

A 0.1 M solution of N-methyl tubuvaline ethyl ester 35 (0.305 g, 1.06 mmol), 1-hydroxybenzotriazole (HOBt) (0.146 g, 1.08 mmol), and Boc-Ile-OH (0.267 g, 1.11 mmol) in CH2Cl2 (10.6 mL) was cooled in a salted ice-water bath. PS-CCD (1.38 mmol/g, 0.920 g, 1.27 mmol) was added with stirring, and the bath was warmed to rt. Stirring was continued for 14 h, the solution was filtered, and the resin was washed with CH2Cl2. The filtrate was then concentrated, diluted with EtOAc, and washed once with sat. NaHCO3 (aq). The aqueous fraction was back-extracted twice with EtOAc, and the combined organic fractions were dried with Na2SO4, filtered, and concentrated to afford intermediate 36, which was taken on without further purification.

Provenance & Evidence