[C:1]([NH:4][C@@H:5]1[C@H:12]([O:13][C:14](=[O:21])[C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[C@@H:11]([CH2:22]Br)[O:10][C@H:7]([O:8][CH3:9])[CH2:6]1)(=[O:3])[CH3:2].C1C=CC=CC=1.CC(C)=O.CCOCC>N1C=CC=CC=1.[Ag]F>[C:1]([NH:4][C@@H:5]1[C@H:12]([O:13][C:14](=[O:21])[C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[C:11](=[CH2:22])[O:10][C@H:7]([O:8][CH3:9])[CH2:6]1)(=[O:3])[CH3:2]A mixture of Compound VI (5 g, 13 mmoles) and dry, technical-grade silver fluoride (5 g, 22.1 mmoles) in dry pyridine (90 ml) was stirred for 14 hours at 25° C, after which time, t.l.c. (2:3 benzene-acetone) showed that all of Compound VI had reacted. The dark solution was poured into ether (500 ml), and the resultant mixture was filtered. The filtrate was evaporated at ≤40° C, and then three 25-ml portions of toluene were added to and evaporated from the residue (to remove all of the pyridine). The resultant syrup was taken up in ether, and the suspension filtered through a small column (250 × 20 mm) of silica get to remove residual silver salts. The effluent was evaporated in vacuo to give the pure Compound VII as a syrup; yield 4 g (100%), [α]D23 +55.2° (c, 1.4, chloroform); νmaxfilm 3420-3290 (NH), 1725 (ester CO), 1660 (Amide I, C=C), 1600, 1585 (monosubstituted phenyl), and 1525 cm-1 (Amide II).
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