Coumarin 3 carboxylic acid

All commercial coumarins (1,2-Benzopyrone 1; 3-Hydroxycoumarin 2; 4-Hydroxycoumarin 3; 6-Hydroxycoumarin 4; 7-Hydroxycoumarin 5; 6,7-Dihydroxycoumarin 6; Coumarin-3-carboxylic acid 7; 3,3′-Methylene-bis-(4-Hydroxycoumarin) 8; 6-Methoxy-7-Hydroxycoumarin 9; and 7,8-Dihydroxy-6-methoxycoumarin 10), reagents, and solvents were purchased from Sigma-Aldrich (Seelze, Germany) and used without further purification. Norfloxacin, erythromycin, and tetracycline were obtained from Sigma Chemical Co., USA, and their stock solutions were then prepared [15 ]. Compounds 11–22 were synthesized according to previously reported procedures [12 (link)]. The stock solutions of coumarin derivatives 1–22 were prepared in DMSO. The highest concentration remaining after broth dilution (4%) did not inhibit bacterial growth, and a positive control with only DMSO 4% was tested and showed no interference with bacterial growth (data not shown).

4,7-Dichloroquinoline 97%, ethylenediamine 99%, hydrazine hydrate 98%, 4,4'-methylenedianiline 97%, triethylamine 99%, coumarin-3-carboxylic acid 99%, were purchased from Sigma Aldrich, MO, USA. Also, reagents as 1,3-Diaminopropane 99%, 1,4-Phenylenediamine, thionyl chloride 97% and solvents as ethanol 98%, dichloromethane 98%, and petroleum ether with 60–80 °C, were supplied from LOBA Chemie, Mumbai, India and used without any further purification. The prepared starting materials such as 9-chloroacridne and 11-chloroneocryptolepine and their corresponding free amines were prepared as reported^{42 (link),43 (link)}.

Benzotriazol-1-yloxy tripyrrolidinophosphonium hexafluoro-phosphate (PyBOP) was purchased from Oakwood Chemical (West Columbia, South Carolina, SC, USA). Coumarin-3-carboxylic acid (99%), 2-amino pyridine (99%), 2-(2ʹ-pyridyl)ethylamine (95%), and trifluoroacetic acid (99%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). 2-(Aminomethyl)pyridine (99%) was obtained from Acros Organic (Belgium, WI, USA). 2-(Aminomethyl)benzimidazole dihydrochloride (98%) was purchased from Alfa Aesar (Ward Hill, USA). N-Boc-ethylenediamine (98%) was purchased from Combi-blocks (SanDiego, CA, USA). All chemicals were used as received without further purification. IR spectra were recorded on Nicolet 6700 FT-IR (Thermo Scientific, Waltham, MA, USA). UV-Vis and fluorescence spectra were measured on Varian Cary Eclipse 5G UV-Vis-NIR spectrometer and Varian Cary Eclipse fluorescence spectrophotometer (CMUSA), respectively. NMR were recorded on Bruker Ascend (Billerica, MA, USA) at 400 MHz for ¹³C and 100 MHz for ¹H, respectively. Mass spectra were obtained on Thermo Scientific Q Exactive spectrometer in high resolution electrospray mode. Single crystal X-ray diffraction was recorded on Bruker Axs Apex Duo Single crystal XRD instrument. ICP-MS was conducted on Agilent Technologies 7700x ICP-MS Analyser (Santa Clara, CA, USA). CLARIOstar plate reader was used for kinetics study.