Lithium Hydroxide → (2s, 4r)-2-Benzoyloxymethyl-1,3-dioxolane-4-carboxylic acid

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To a solution of methyl-2-(R,S)-benzoyloxymethyl-1,3-dioxolane-4-(R)-carboxylate (III), (411 g, 1.54 mmol, 1 eq., 2:1 mixture of cis and trans isomers) in a 1:1 mixture of tetrahydrofuran (THF) and water, lithium hydroxide (LiOH) (64.8 g, 1.54 moles, 1 eq) was added portion wise over a period of 30 min., keeping the reaction flask temperature below 30° C. After 90 min., THF was removed by vacuum and the aqueous solution was acidified to pH=2.5-3.2, by dropwise addition of 30% (w/w) sulphuric acid. The resulting solution was extracted with dichloromethane (4×400 mL). The combined organic phase was washed with brine, dried over sodium sulphate and concentrated to produce 380 g of a dark oil. The isomers were separated by column chromatography on silica gel, using 2% acetic acid in dichloromethane to produce 220 g of the cis isomer (IVa) (56.5%) and 116 g of the trans isomer (IVb) (30%). Each of isomers was independently used for next step.

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