Novel examples of N-methyl effect on cyclisation of N-Boc derivatives of amino alcohols. A theoretical study

New examples of the N-methyl effect on the cyclisation of N-tert-butoxycarbonyl derivatives of amino alcohols are reported. Ab initio studies for the displacement step with formation of the five-membered heterocycle indicate that the increase of the nucleophile character of the carbonyl oxygen of the carbamate group with the N-methyl substitution is responsible for the acceleration of the cyclisation step.