Toward the total synthesis of Sinefungin

Among many attempts toward the total synthesis of Sinefungin one of the most promising approach was found to be the transglycosylation of the amino acid-D-ribofuranosyl portion of 15 to N6-acyladenine. The key intermediate (15) was prepared from uridine in 12 steps. Thus, treatment of 2',3'-O-isopropylidene-uridine 5'-aldehyde (5) with methyl 4-nitrobutanoate gave rise to an aldol adduct (6) which was led to 4-nitro-4-(5'-deoxy-2', 3'-O-isopropylideneuridin-5'-yl)-butanal (10) via 8. A four-component condensation involving 10 afforded N,N-disubstituted alpha-aminocarboxamide derivative (11). The transglycosylation involving 8 and N6-benzoyladenine was successfully achieved. A parallel transglycosylation involving 15 and N6-benzoyladenine is under way to obtain 16.