合成路线1

A new synthesis of ddI has been described: The reaction of inosine (I) with 2-acetoxyisobutyryl bromide (II) gives a mixture of two bromodiacyloxy derivatives (IIIa) and (IIIb) that, without separation, are hydrolyzed either with ammonia in methanol or with the pair Zn-Cu in the same solvent, yielding a mixture of the 2- and 3-bromo derivatives (IVa) and (IVb). The acylation of this mixture with chlorothionoformic acid O-phenyl ester and dimethylaminopyridine (DMAP) in acetonitrile gives a new mixture of the thiono esters (Va) and (Vb), which is treated with tributyltin hydride and azoisobutyronitrile (AIBN) in refluxing benzene to yield 5'-O-(2-acetoxyisobutyryl)-2',3'-didehydro-2',3'-dideoxyinosine (VI). The hydrolysis of (VI) with ammonia in methanol affords 2',3'-didehydro-2',3'-dideoxyinosine (VII), which is finally hydrogenated with H2 over Pd/C.