Urethanes find extensive use as protecting groups for amines. These protecting groups are easily formed (see below) and can be readily removed using the appropriate conditions. Several very popular urethane protecting groups have been developed that withstand a variety of harsh reaction conditions but are readily removed when subjected to mild acid, hydrogenolysis or mild basic media.
|
Protecting Group |
Cleavage Conditions |
||||||
|
TFA |
HBr/TFA |
H2/Pd-C |
Piperidine/DMF |
|||
|
y | y | n | n | |||
|
|
n | y | y | n | ||
|
|
n | y | n | y | ||
The different cleavage conditions of the above urethane protecting
groups has enabled so-called ‘orthogonal’ protection strategies
to be developed that enable selective chemistries to be performed upon different
amines present in the same molecule (for example peptide synthesis).
