Boron trifluoride etherate → (2S,4R)-4-tert-butoxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid benzyl ester

Participants

Reaction Conditions

Reaction Steps

Tert-Butyletherification: To a solution of (2S,4R)-4-hydroxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid benzyl ester (14.8 g) in dichloromethane (140 ml) were added boron trifluoride ethyl etherate (3 ml) and isobutylene (cooled and liquefied at −30° C., 170 ml) at −30° C. The turbid reaction mixture was stirred at −20° C. for 2 h, poured onto a saturated sodium bicarbonate solution, and extracted with dichloromethane. The organic phases were washed with water, dried over magnesium sulphate and concentrated. The residue was chromatographed on silica gel using EtOAc/hexane 1:4 and 1:2 as eluents to obtain (2S,4R)-4-tert-butoxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid benzyl ester (16.4 g) as a glassy syrup, MS: 467 (M).

Provenance & Evidence