Citric Acid → (2S,4R)-2-hydroxymethyl-4-tritylsulfanyl-pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

Ester reduction, Method B: A solution of 35 g (69 mmol) (2S,4R)-4-Tritylsulfanyl-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester in 380 ml toluene/60 ml THF was treated at −47° C. to −50° C. with 44 g (152 mmol) of a 70% solution of sodium dihydrido-bis(2-methoxy-ethoxo)aluminate in toluene (3.5 M Red-Al in toluene). After 3 h at −50° C. and 1 h at −30° C. the solution was poured into water (1 l) with 40 g of citric acid and extracted with EtOAc (2×). The organic phase was dried over Na2SO4 and evaporated. Column chromatography on silica gel with hexane/EtOAc (7:3) gave 23.0 g (69%) (2S,4R)-2-hydroxymethyl-4-tritylsulfanyl-pyrrolidine-1-carboxylic acid tert-butyl ester, MS: 476 (MH+).

Provenance & Evidence