Abstract
OxymaPure (ethyl 2-cyano-2-(hydroxyimino)acetate) was tested as an additive for use in the carbodiimide (DIC) approach for the synthesis of a novel series of α-ketoamide derivatives (4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino]benzoyl amino acid ester derivatives). OxymaPure showed clear superiority to HOBt/DIC or carbodiimide alone in terms of purity and yield. The title compounds were synthesized via the ring opening of N-acylisatin. First, N-acetylisatin was reacted with 4-aminobenzoic acid under conventional heating as well as microwave irradiation to afford 4-(2-(2-acetamidophenyl)-2-oxoacetamido)benzoic acid. This α-ketoamide was coupled to different amino acid esters using OxymaPure/DIC as a coupling reagent to afford 4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino]benzoyl amino acid ester derivatives in excellent yield and purity. The synthesized compounds were characterized using FT-IR, NMR, and elemental analysis.
Highlights
Introduction αKetoamides are compounds of interest in organic chemistry and are present in many active pharmaceutical compounds [1,2,3,4,5,6]
1-Acetylindoline-2,3-dione (N-acetylisatin, 1) was initially prepared by reaction of isatin with acetic anhydride, using conventional heating under the same conditions as those described in the literature [30,31]
We demonstrate that the use of a microwave irradiation, using a multimode reactor (Synthos 3000, Anton Paar GmbH, Graz, Austria, 1,400 W maximum magnetron, method B; Experimental section), renders 1 from isatin and acetic anhydride (Scheme 2) in excellent yield in less reaction time and higher purity than the conventional method, as observed from spectral data
Summary
Ketoamides are compounds of interest in organic chemistry and are present in many active pharmaceutical compounds [1,2,3,4,5,6]. Parallel with the application of the α-ketoamide moiety in medicinal chemistry, numerous synthetic methods have been described [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. N-acetylisatin (1) by the attack of an amine at C2-carbonyl group of N-acetylisatin (Scheme 1) [22,23,24,25,26,27]. General mechanism for the reaction of N-acylisatin (1) with amines
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