Some benzylidene acetal derivatives of theophylline nucleosides

The reaction of some hexopyranosyltheophylline nucleosides with benzaldehyde in the presence of zinc chloride gave the expected benzylidene acetals. Thus, 7-alpha-D-mannopyranosyltheophylline gave the 2',3':4',6'-diacetal as a mixture of diastereoisomers, one of which was isolated. The beta-D-galacto- and beta-D-gluco-pyranosyltheophyllines gave the 4',6'-acetals, which were characterised as 2',3'-diesters. Mild, acidic hydrolysis of 7-(4,6-O-benzylidene-2,3-di-O-mesyl-beta-D-glucopyranosyl)theophylline gave 7-(2,3-di-O-mesyl-beta-D-glucopyranosyl)theophylline, and strongly basic hydrolysis gave 7-(2,3-anhydro-4,6-O-benzylidene-beta-D-allopyranosyl)theophylline. Ring-opening of this 2',3'-epoxide with iodide anion afforded mainly 7-(4,6-O-benzylidene-2-deozy-2-iodo-beta-D-altropyranosyl)theophylline, which was characterised as the 6'-acetate.