Propionic Acid → 3(R)-[(4-Benzyloxyphenyl)methyl]-5(S)-[1(S)-(Boc-amino)-2-cyclohexylethyl]dihydrofuran-2-one

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Reaction Steps

In analogy with Example 1h), 5.2 g (16.7 mmol) of 5(S)-[1(S)-(Boc-amino)-2-cyclohexylethyl]dihydrofuran-2-one (Example 12a)), dissolved in 50 ml of THF, are deprotonated, at -70° C., with 33.4 ml of a 1M solution of lithium bis(trimethylsilyl)amide in THF, and alkylated (at -75° C. for 1 h) with 5.2 g (16.07 mmol) of p-benzyloxybenzyl iodide [preparation, see Example 1d)] in 15 ml of THF. Adding 6.2 ml (83.02 mmol) of propionic acid and water at -75° C., and further working up, affords the title compound after column chromatography (SiO2, hexane/ethyl acetate: 4:1). TLC Rf (hexane/ethyl acetate: 4:1)=0.27; tRet (II)=20.41 min.

Provenance & Evidence