Specific solvation as a tool for the N-chemoselective arylsulfonylation of tyrosine and (4-hydroxyphenyl)glycine methyl esters

The methyl esters of L-tyrosine and D-(4-hydroxyphenyl)glycine were directly N-functionalized in a chemoselective fashion, without protecting the phenolic hydroxy group, by reaction in THF with arylsulfonyl chlorides (aryl = 2-nitrophenyl-, 4-nitrophenyl-, 4-tolyl), using lyophilized sodium carbonate as a base and in the presence of small amounts of DMF that, through specific solvation, deactivates the phenolic oxyanion