[C:1]([O:9][CH2:10][C@H:11]1[S:15][CH:14]([N:16]2[CH:31]=[CH:30][C:20]([NH:21][C:22](=[O:29])[C:23]3[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=3)=[N:19][C:17]2=[O:18])[CH2:13][O:12]1)(=[O:8])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1>CO>[C:1]([O:9][CH2:10][C@H:11]1[S:15][C@@H:14]([N:16]2[CH:31]=[CH:30][C:20]([NH:21][C:22](=[O:29])[C:23]3[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=3)=[N:19][C:17]2=[O:18])[CH2:13][O:12]1)(=[O:8])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1To the crude (R)-benzoyloxymethyl-4-(R,S)-(N-benzoylcytosin-1-yl)-1,3-oxathiolane (8.0 g) in a 100 mL round bottom flask, was added approximately 14.0 times (by volume) methanol (112 mL) and the mixture was refluxed till a clear solution could be seen. This was then allowed to cool without stirring overnight. The resulting crystallized product was then filtered, followed by washing with methanol (50 mL). Once all the mother liquor and the subsequent washing had passed through, the resulting crystallized white product was re-washed slowly with methanol (2×100 mL) and dried under vacuum. The resulting white crystalline solid on analyzing with NMR showed that it is >99% the cis isomer. Isolated yield, 3.36 g (42% yield for the recrystallization, based on the crude). Optical purity: RR/SS: 98.1/1.9.
Wird geladen…