New base‐labile amino‐protective groups for peptide synthesis

Modification of the methyl group in 2‐(methylsulphonyl)ethanol gave alcohols which could be used to introduce amino‐protective groups of the urethane type, which are labile in alkaline media. The cleavage involves β‐elimination. Exchange of the methyl group by a phenyl group bearing a function with a negative inductive effect (NO2 or MeSO2) afforded protecting groups with a higher sensitivity to base. The recommended function is a disulphone: 2‐[4‐(methylsulphonyl)phenylsulphonyl]ethanol. The function has a somewhat better stability than the Fmoc group, resists catalytic hydrogenolysis, is highly stable in acidic medium and its elimination product does not polymerize spontaneously. The suggested designation of the new protective group is Mpc.