[g_orbital]

As shown in the following scheme (taken from J. Org. Chem. 1996, 61, 5208-5209), glucopyranose (15) was protected by acetic anhydride to form the triacetyl compound (16). Treatment of (16) with BnNH₂ (Benzylamine), followed by hydrolysis with dilute aqueous acid furnished the pyranose (17).

As you can see, there was a selective hydrolysis which only removed the C-1 O-acetyl (at the anomeric position) while the two other O-acetyl groups were not affected. The author indicates that the reaction with benzylamine forms "amino glycoside", but I can't understand how and why. My question is: What is the mechanism of this deprotection - is it just a simple "addition-elimination" process, and if so - why does benzylamine react regioselectively with the C-1 O-acetyl group, and how does the "amino glycoside" look like? Also, what is the role of the hydrolysis with HCl_(aq) in terms of mechanism?

Thank you very much in advance!

[movies]

Sounds like an oxocarbenium mechanism to me.

[g_orbital]

Movies, may you please elaborate on this oxocarbenium mechanism? At which step is this oxocarbenium ion created? And again, how do I get regioselectivity in this rxn? Thanks!

[movies]

There is probably an oxocarbenium intermediate in both parts of step b.  The selectivity comes from the fact that in making the first oxocarbenium you kick out -OAc from the anomeric position.  The rest of the OAc groups are unaffacted.