Discussion:
Deprotection of Cbz group
(too old to reply)
Palas
2006-04-19 23:47:59 UTC
Hello everybody,

I would like to know how to deprotect the Cbz group from arginine. Is
there any method other than using hydrogenation reaction with
palladised carbon or palladium hydroxide.

If there is a method then can anyone tell me the rpocedure for it.

I would be greatful if you help me out in this.
Thanks
Palas
Jimchip
2006-04-20 01:38:00 UTC
Post by Palas
Hello everybody,
I would like to know how to deprotect the Cbz group from arginine. Is
there any method other than using hydrogenation reaction with
palladised carbon or palladium hydroxide.
If there is a method then can anyone tell me the rpocedure for it.
I would be greatful if you help me out in this.
Thanks
Palas
I've heard of acid and thioanisole but I've never done it. What's wrong with
catalytic hydrogenation?
--
just curious
l***@sbcglobal.net
2006-04-20 02:49:18 UTC
Post by Jimchip
Post by Palas
Hello everybody,
I would like to know how to deprotect the Cbz group from arginine. Is
there any method other than using hydrogenation reaction with
palladised carbon or palladium hydroxide.
If there is a method then can anyone tell me the rpocedure for it.
I would be greatful if you help me out in this.
Thanks
Palas
I've heard of acid and thioanisole but I've never done it. What's wrong with
catalytic hydrogenation?
No personal experience, but Greene and Greene say that the standard
non-hydrogenation method for cleaving carbamates is base, not acid (N-phenyl
carbamate protecting an alcohol in specific--hydrogenolysis won't work in
that case, absent a benzylic C-N or C-O bond). Of course, that may be
because they're talking about carbamates used in nucleotide synthesis, and
nucleobases are susceptible to acid cleavage. They also say that carbamates
are less susceptible than ordinary esters to hydrolysis, so you may have to
beat on it, either way. Also, in argnine, I would also watch out for
guanidine cleavage under hydrolytic conditions.

Eric Lucas
Jimchip
2006-04-20 04:15:55 UTC
Post by l***@sbcglobal.net
Post by Jimchip
Post by Palas
Hello everybody,
I would like to know how to deprotect the Cbz group from arginine. Is
there any method other than using hydrogenation reaction with
palladised carbon or palladium hydroxide.
If there is a method then can anyone tell me the rpocedure for it.
I would be greatful if you help me out in this.
Thanks
Palas
I've heard of acid and thioanisole but I've never done it. What's wrong with
catalytic hydrogenation?
No personal experience, but Greene and Greene say that the standard
non-hydrogenation method for cleaving carbamates is base, not acid (N-phenyl
carbamate protecting an alcohol in specific--hydrogenolysis won't work in
that case, absent a benzylic C-N or C-O bond). Of course, that may be
because they're talking about carbamates used in nucleotide synthesis, and
nucleobases are susceptible to acid cleavage. They also say that carbamates
are less susceptible than ordinary esters to hydrolysis, so you may have to
beat on it, either way. Also, in argnine, I would also watch out for
guanidine cleavage under hydrolytic conditions.
Eric Lucas
I don't think so. Carbamates can undergo base cleavage but, at least as far
as amino acid protection is the topic, both Cbz and Boc undergo SN1 decomp.
under acidic conditions--Boc with dry TFA, Cbz with (dry) HBr/TFA (stronger
acid required). But there's still nothing wrong with hydrogenolysis of Cbz.
--
unless there's something weird about the already weird arginine