Citric Acid → HCID 10970865, compound

Participants

Reaction Steps

10.2 g of 5(S)-[1(S)-(Boc-amino)-2-cyclohexylethyl]-3(R,S)-ethoxycarbonyl-dihydrofuran-2-(3H)-one are reacted at RT with 5.39 g of p-fluorobenzyl bromide (Fluka, Buchs, Switzerland) and 0.68 g of sodium in 180 ml of ethanol. Because, according to TLC, not all of the lactone has reacted after 1.5 h, a further 0.2 g of sodium and 0.7 g of p-fluorobenzyl bromide are added. After 16 h, the batch is poured onto a mixture of 10% citric acid and ice and extracted 3 times with ether. The organic phases are washed twice with water and twice with brine, dried with Na2SO4 and concentrated by evaporation. After the addition of hexane/ethyl acetate, some of the oily crude product crystallises out under the effect of ultrasound to give the title compound (ratio of diastereoisomers 4:1). Column chromatography (SiO2, hexane/ethyl acetate 4:1) of the mother liquor yields more title compound (ratio of diastereoisomers approximately 1:4). TLC Rf (C)=0.29; FAB-MS (M+H)+ =492.

Provenance & Evidence