Nucleoside analogues from push-pull functionalized branched-chain pyranosides

Abstract

The reaction of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro- hexopyranosid-3-ulose (1) with ethynylmagnesium bromide in tetrahydrofuran and subsequent trimethylsilylation yielded the methyl 4,6-O-benzylidene-2-deoxy-3-C- ethynyl-3-O-trimethylsilyl-α-D-ribo-hexopyranoside (3). Push-pull functionalization of 3 with N,N,N′,N′,N″,N″- hexamethylguanidinium chloride under basic conditions and following deprotection afforded the spiro{2,5-dihydro-3-dimethylamino-furan-2,8'-4',4'a,6',7',8',8'a- hexahydro-6'-methoxy-2'-phenyl-pyrano[3,2-d][1,3]dioxine}-5- ylidenemalononitrile (9). Furthermore, compound 1 reacted with N,N-dimethylformamide dimethylacetal to furnish methyl (E)-4,6-O-benzylidene-2- deoxy-2-dimethylaminomethylene-α-D-erythro-hexopyranosid-3-ulose (10). Treatment of 10 with methylhydrazine and amidines yielded (4S,5aR,8R,9aS)-2,5a, 6,9a-tetrahydro-4-methoxy-2-methyl-8-phenyl-4H-[1,3]dioxino[4',5':5,6]pyrano[4, 3-c]pyrazole (11a) and (2R,4aR,6S,10bS)-4,4a,6,10b-tetrahydro-6-methoxy-2- phenyl[1,3]dioxino[4',5':5,6]pyrano[4,3-d]pyrimidines 12, respectively. © 2006 Verlag der Zeitschrift für Naturforschung.