C1(S[O:8][C:9](=O)[CH:10]([CH:26]([OH:28])[CH3:27])[CH:11]([NH:18][CH2:19][C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=2)[C:12]#[C:13][Si](C)(C)C)C=CC=CC=1.[OH-].[K+].Cl.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.C1C=C(SSC2N=CC=CC=2)N=CC=1>C1COCC1.C(#N)C>[CH2:19]([N:18]1[CH:11]([C:12]#[CH:13])[CH:10]([CH:26]([OH:28])[CH3:27])[C:9]1=[O:8])[C:20]1[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=1There was dissolved 2.054 g (5.0 mmol) of 3-benzylamino-2-(1-hydroxyethyl)-5-trimethylsilyl-4-pentinic acid phenylthioester in 40 ml of THF, to which 3 ml of 4 N potassium hydroxide was added and the mixture was stirred at room temperature for 3 hours. The reaction mixture was neutralized with 2 N hydrochloric acid and was extracted six times with ethyl acetate while conducting salting-out. The extract was dried with anhydrous magnesium sulfate and concentrated. There was added 250 ml of acetonitrile to the concentrated solution, and then 1.57 g (60 mmol) of triphenylphosphine was added, to which 1.32 g (6.0 mmol) of 2,2'-dipyridyldisulfide in 50 ml of acetonitrile was added dropwise for 40 minutes while vigorously stirring with heating under reflux. After the solution was further heated under reflux for 1 hour, the obtained reaction mixture was concentrated, followed by purification with 50 g of silica-gel column-chromatography (eluent; methylene chloride→diethyl ether) and then with 50 g of silica-gel column-chromatography (eluent;hexane:diethyl ether=1:4) to give 801 mg of a trans-form and 62 mg of a cis-form of 1-benzyl-4-ethynyl-3-(1-hydroxyethyl)-2-azetidinone.
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