Methanesulfonic Acid → (4S,2S)-4-Methanesulfonyloxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid methylester

Participants

Reaction Conditions

Reaction Steps

Via Mesylate: A biphasic solution of 13.9 ml (215 mmol) methanesulfonic acid, 29.8 ml (215 mmol) triethylamine and 58.7 g (224 mmol) triphenylphosphine in 150 ml toluene was added to a suspension of 60 g (179 mmol) (2S,4R)-4-hydroxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid methyl ester in 300 ml toluene which was stirred mechanically. After adding 44.9 ml (233 mmol) of diisopropyl azodicaboxylate (exothermic!) the solution was heated for 2.5 h at 80° C. 300 ml water was added at room temperature and extracted with EtOAc (3×300 ml). The organic phase was washed with aqueous 10% KHSO4 (2×100 ml), 10% NaCl (2×150 ml) dried over Na2SO4 and evaporated to give 180 g of crude product. Flash chromatography (EtOAc/hexane 1:1) gave 63.7 g (86%) of (4S,2S)-4-methanesulfonyloxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid methylester.

Provenance & Evidence