Citric Acid → (2S,3R)-1-t-butyldimethylsilyl-3-benzyl-4-oxo-2-azetidinecarboxylic acid

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Reaction Conditions

Reaction Steps

In 6 ml of THF was dissolved 836.3 mg of diisopropylamine and the solution was cooled to 0° C. in a nitrogen atmosphere. To the solution was gradually added 5.2 ml of a n-hexane solution containing 530 mg of n-butyl lithium at 0° C. The mixture was stirred for 10 minutes at the same temperature. Then, a solution of 920 mg of (S)-1-t-butyldimethylsilyl-4-oxo-2-azetidinecarboxylic acid (1) in 8 ml of dry THF was added to the mixture at 0° C. followed by stirring at room temperature for 30 minutes. The solution was cooled to 0° C. and 820.8 mg of benzyl bromide was added to the solution. The mixture was then stirred at room temperature for 30 minutes. The solution was again cooled to 0° C. and a 10% citric acid solution was added thereto to render acidic. Ether was added to the mixture to separate from the aqueous phase. After the ethereal phase was dried, the solvent was removed by distillation to obtain 858 mg of (2S,3R)-1-t-butyldimethylsilyl-3-benzyl-4-oxo-2-azetidinecarboxylic acid (2) showing a melting point of 99°~102° C. as colorless crystals.

Provenance & Evidence