Am 400

Suspensions of 1,5-dihydroxynaphthalene (1; 1.25 mmol), rose bengal (20 mg; 0.02 mmol), and water (150 mL) were exposed to green LEDs for 5 h while a gentle stream of air was bubbled through the solution. Thereafter, phenylamines 3 (1.5 mmol) were added and the solutions were stirred for 4 h at room temperature (RT). Work-up of the reaction mixtures followed by column chromatography over silica gel (3 : 1 petroleum ether/ethyl acetate) provided pure compounds 4–15 (Scheme 1; Figure 1).
All reagents were of commercial quality and used without further purification. The melting points were measured in a Stuart Scientific SMP3 equipment. The IR spectra were obtained in a vector 22-FT Bruker spectrophotometer using KBr disks, and wavelengths are expressed in cm⁻¹. Proton nuclear magnetic resonance (¹H NMR) spectra were measured at 400 and 300 MHz in a Bruker AM-400 and Ultrashield-300 spectrometers. Chemical shifts are expressed in ppm using TMS as an internal reference (δ scale), and (J) coupling constants are expressed in hertz (Hz). Carbon-13 nuclear magnetic resonance (¹³C NMR) spectra were measured at 100 and 75 MHz in a Bruker AM-400 and Ultrashield-300, spectrometers. Silica gel (70–230 and 230–400 mesh) and TLC on aluminum foil 60 F₂₅₄-supported silica (Merck, Darmstadt) were used for the chromatography analytical columns and TLC, respectively.

Proton nuclear magnetic resonance (¹H NMR) spectra were recorded on a Bruker AM 400 (400 MHz) spectrometer. Chemical shifts are expressed in parts per million (ppm) and calibrated on characteristic solvent signals as internal standards. Carbon nuclear magnetic resonance (¹³C NMR) spectra were recorded on a Bruker AM 400 (101 MHz) spectrometer.

All reagents and solvents should meet the standards of analytical reagent before use, and the melting points of all the synthesized compounds were determined in open capillaries using Shengyan electrothermal PIF YRT-3 apparatus without correction. Bruker AM-400 was applied to record ¹H NMR and ¹³C NMR spectra, and LCQ Deca XP plus was used to determine the ESI/MS spectra. In this study, human cancer cell lines A549, MCF-7, HepG2, Hela and the normal cell WI-38 were purchased from Cell Resources Center of Shanghai Institutes for Biological Science (Chinese Academy of Sciences), which were cultured on the basis of supplier's instructions. DMEM (Dulbecco's modified Eagle medium), FBS (fetal bovine serum) were obtained from Hyclone (Shanghai, China), and MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] were provided by Sigma (Beijing, China).
All reagents and solvents are reagent level or are purified by standard methods prior to use. HDAC Inhibitor Drug Screening Kit was purchased from BioVision, and acetyl-histone H3, acetyl-α-tubulin and β-actin were obtained from AFFINITY BIOSCIENCE. Fluor de Lys^® HDAC1 Assay kit (BML-AK511, Enzo^® Life Sciences) and Fluor de Lys^® HDAC6 Assay kit (BML-AK516, Enzo^® Life Sciences) were applied to determine the inhibitory activities of the compounds against HDAC1 and HDAC6 subtypes.