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Anticancer Agents, 15. Squaric Acid Diethyl Ester: A New Coupling Reagent for the Formation of Drug Biopolymer Conjugates. Synthesis of Squaric Acid Ester Amides and Diamides
Author(s) -
Tietze Lutz F.,
Arlt Michael,
Beller Matthias,
Gl üsenkamp KarlHeinz,
Jähde Eckhard,
Rajewsky Manfred F.
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240539
Subject(s) - chemistry , squaric acid , amide , triethylamine , organic chemistry , reagent , dichloromethane , amine gas treating , phenoxazine , combinatorial chemistry , solvent , medicine , phenothiazine , pharmacology
Reaction of squaric acid diethyl ester ( 1 ) with a slight excess of a primary or secondary amine 2 in ethanol, dichloromethane or aqueous buffer (pH 7) at 20°C for 0.3–12 h gives the squaric acid amide esters 3 in mostly excellent yields. Treatment of 3 with amines 2 or 4 in organic solvents in the presence of triethylamine or in aqueous buffer (pH 9) leads to the corresponding symmetrical and unsymmetrical squaric acid diamides 5 , respectively. The reaction can be followed by UV spectroscopy.