Sodium hydride → 2,3-dibenzyl 3-tert-butyl 1-cyclopropyl-4-(3,4,4-trimethyl-2,5-dioxo-1-imidazolidinyl)-2(R),3(R,S),3-butanetricarboxylate

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Reaction Steps

A solution of 6.4 g of 2,3-dibenzyl 3-tert-butyl 1-cyclopropyl-2(R),3(R,S),3-propanetricarboxylate (1:1 mixture of diastereoisomers) in 30 ml of 1,2-dimethoxyethane was treated with 0.446 g of an 80% dispersion of sodium hydride in mineral oil. The mixture was stirred at room temperature for 30 minutes. A solution of 3.84 g of 1-(bromomethyl)-3,4,4-trimethyl-2,5-imidazolinedione in 20 ml of 1,2-dimethoxyethane was added dropwise over 15 minutes. The mixture was stirred at room temperature for 36 hours, the solvent was evaporated and the residue was dissolved in ethyl acetate and washed with water and saturated sodium chloride solution. After drying over anhydrous magnesium sulphate the solvent was evaporated. The residue was purified by flash chromatography on silica gel using hexane/ethyl acetate (7:3) and subsequently hexane/ethyl acetate (6:4) for the elution to give 6.4 g of 2,3-dibenzyl 3-tert-butyl 1-cyclopropyl-4-(3,4,4-trimethyl-2,5-dioxo-1-imidazolidinyl)-2(R),3(R,S),3-butanetricarboxylate as a 1:1 mixture of diastereoisomers in the form of a clear oil.

Provenance & Evidence