Citric Acid → 5(S)-(Boc-Amino)-4(S)-hydroxy-6-cyclohexyl-2(R)-[(p-methoxyphenyl)methyl]hexanoic acid

Participants

Reaction Steps

1000 ml of 1M aqueous LiOH solution are added, under a protective gas, to a solution of 103 g (239 mmol) of 5(S)-[1(S)-(Boc-amino)-2-cyclohexylethyl]-3(R)-[(p-methoxyphenyl)methyl]dihydrofuran-2-(3H)-one in 800 ml 1,2-dimethoxyethane. After 3 h at RT, the reaction solution is poured onto an ice-cold mixture of 1.5 l of sat. NH4Cl solution, 1 l of 10% citric acid solution and 2 l of ether. The aqueous phase is separated off and extracted 2× with 1 l of ether on each occasion. The organic phases are washed 4× with ice-water and finally with saline. Drying with sodium sulfate and evaporating yields the title compound from the organic phases: tRet (II)=16.0 min; FAB-MS (M+H)+ =450.

Provenance & Evidence