CC(C)([O-])C.[K+].[C:7]([NH:10][C:11]1[CH:12]=[CH:13][CH:14]=[C:15]2[C:20]=1[C:19](=[O:21])[CH2:18][CH2:17][CH2:16]2)(=[O:9])[CH3:8].[N:22](OCCCC)=[O:23].Cl>O1CCCC1.C(OCC)(=O)C.CCCCCC>[C:7]([NH:10][C:11]1[CH:12]=[CH:13][CH:14]=[C:15]2[C:20]=1[C:19](=[O:21])[C:18](=[N:22][OH:23])[CH2:17][CH2:16]2)(=[O:9])[CH3:8]To a reaction solution obtained by suspending 316 mg of potassium tert-butoxide in 18 ml of tetrahydrofuran (hereinafter abbreviated as THF) and cooling the suspension to 0° C. under a nitrogen stream was added a solution of 500 mg of the compound prepared in (1) above in 2 ml of THF, a bit at a time. After stirring for 10 minutes at the same temperature and an addition of 0.35 ml of butyl nitrite, the mixture was heated at 50° C. for 1 hour while stirring. Precipitates obtained by the addition of diethyl ether to the reaction mixture were collected by filtration. The powder thus obtained was suspended into a 10% aqueous solution of hydrochloric acid and extracted with ethyl acetate. The extract was washed with brine and dried over magnesium sulfate. The residue obtained by the concentration of the solvent was subjected to silica gel column chromatography using an ethyl acetate-hexane (1:1) mixed solvent as an eluant to obtain fractions containing the target compound. The fractions were concentrated to produce 320 mg of the title compound.
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