Facile Deprotection of O-Cbz-Protected Nucleosides by Hydrogenolysis:  An Alternative to O-Benzyl Ether-Protected Nucleosides

[reaction: see text] Because of side-reactions encountered during hydrogenolysis, benzyl ethers are usually not an effective protecting group for nucleosides. Benzyloxycarbamates provide an alternative to traditional benzyl ethers for protection of nucleoside hydroxyl groups, as they are much more labile to hydrogenolysis. Deprotection conditions using transfer hydrogenolysis are described that avoid the reduction of the pyrimidine nucleobase during deblocking of O-Cbz-protected nucleosides. Additionally, an experiment is described that suggests the nucleobase component of a nucleoside is responsible for the sluggish hydrogenolysis of nucleosides.