pH-Controlled Selective Protection of Polyaza Macrocycles

Authors:
  • ZKZoltan Kovacs
    Zoltan Kovacs
  • ASA. Dean Sherry
    A. Dean Sherry
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Abstract
Piperazine (1), tetraazacyclododecane 3 and pentaazacyclopentadecane 4 react with chloroformates in acid solution to give the selectively protected carbamate derivatives 1a, 3a-d, and 4a. The benzyloxycarbonyl derivatives 3d and 4a were alkylated with tert-butyl bromoacetate and removal of the benzyloxycarbonyl protection by catalytic hydrogenation afforded tert-butyl esters 5b and 6b in good yields.