652972-83-3Relevant academic research and scientific papers
Chemoselective N-alkylation of Di-N,O-protected tyrosine through specific oxy-anion solvation by non-hydrogen bonding donor solvents
Penso, Michele,Albanese, Domenico,Landini, Dario,Lupi, Vittoria,Scaletti, Davide
, p. 741 - 744 (2006)
N-(2-Nitro-benzenesulfonyl) activated L-tyrosine methyl ester has been directly N-alkylated under solid-liquid phase-transfer catalysis (SL-PTC) conditions and in a coordinating non-hydrogen bonding donor (non-HBD) solvent, which reduces through specific
Specific Solvation as a Tool for the N-Chemoselective Arylsulfonylation of Tyrosine and (4-Hydroxyphenyl)glycine Methyl Esters
Penso, Michele,Albanese, Domenico,Landini, Dario,Lupi, Vittoria,Tricarico, Giovanni
, p. 4513 - 4517 (2007/10/03)
The methyl esters of L-tyrosine and D-(4-hydroxyphenyl)glycine were directly transformed into the corresponding 2-aryl-sulfonamido esters with arylsulfonyl chlorides, without protecting the phenolic hydroxy group. The reaction is conducted in a THF/DMF (8:1) mixture as solvent, and using lyophilized solid sodium carbonate as base. The N-arylsulfonylation takes place with good yields (62-85%) in a chemoselective fashion, without racemization of the stereogenic carbon centers. The DMF (2.6 mol/mol amino ester) specifically solvates the oxygen atom of the formed N,O-dianion, reducing its nucleophilicity and dramatically increasing the chemoselectivity of the N-substitution. In contrast, in the absence of a highly coordinating additive, the phenoxide anion competes unfavorably with the 2-amino group for the nucleophilic attack, and the N,O-disulfonyl esters are produced with relevant yields. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
