New Amine Protecting Group

Scientists at Pfizer have recently published a new protecting group for amines – the Mpoc group.  This is essentially the Boc group where two methyl groups have been joined together to form a cyclopropane ring, but this minor change in structure results in a large change in stability / reactivity.  The preparation and use of the reagent is shown below.

The stability of secondary carbamate (4) and tertiary carbamate (5) were studied and were found to be completely stable to acidic, basic, nucleophilic, oxidising and reducing conditions.  In particular it is stable in the presence of strong acids such as HBr/AcOH, neat TFA, HCl in dioxan, the typical conditions for removing a Boc group.

It can be removed by treatment with NBS and TFA.

E.J. Snider and S.W. Wright,* Tet. Letts., 2011, 52, 3171-3174.