p-Toluenesulfonic acid → 2-{1 (S)-tert-butoxycarbonylamino-3(S)-isopropyl-4-[4-methoxy-3-(3-methoxypropyloxy)-phenyl]-butyl}-4(R)-methyl-tetrahydrofuran-5-one

Participants

Reaction Steps

2.02 g of p-toluenesulfonic acid (monohydrate) are added to 5.6 g of 5(S)-tert-butoxycarbonylamino-4(S)-hydroxy-7(S)-isopropyl-2(R)-methyl-8-[4-methoxy-3-(3-methoxy-propyloxy)-phenyl]-octanoic acid (N-butyl)-amide (Example 32) in 240 ml of chloroform at room temperature and the mixture is stirred at room temperature for a further 18 hours. The reaction mixture is concentrated by evaporation and the residue is partitioned between diethyl ether and 0.1N hydrochloric acid. The organic phases are concentrated by evaporation and the title compound is obtained from the residue after FC (160 g of silica gel, eluant: ethyl acetate/hexane 1:1): Rf (ethyl acetate/hexane=2:1)=0.47; m.p. 86°-87° C.

Provenance & Evidence