Nitrophenyl-group-containing Heterocycles. Part I. Synthesis, Characterization, Anticancer Activity and Antioxidant Properties of Some New 5,6,7,8-tetrahydroisoquinolines Bearing 3(4)-nitrophenyl Group

Regioselective cyclocondensation of 2,4-diacetyl-5-hydroxy-5-methyl-3-(3-nitrophenyl/4-nitrophenyl)cyclohexanones 1a,b with cyanothioacetamide fforded the corresponiing 7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(3-nitrophenyl/4-nitrophenyl)-5,6,7,8-tetrahydro-soquinoline-3(2H)-thiones 2a,b in 93-96%. Reaction of compounds 2a,b ethyl iodide, 2-chloroacetamide or N-(naphthalen-1-yl)-2-chloroacetamide (5) in the presence of sodium acetate gave the corresponding p(5,6,7,8-tetrahydroisoquinolin-3-yl)thio derivatives 3a,b, 4a,b and 6a,b. In a similar manner, reaction of a,b with other N-aryl-2-chloroacetamides 7a-d gave 2-[(7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(3-nitrophenyl/4-nitrophenyl)-5,6,7,8-tetrahydroisoquinolin-3-yl)thio]-N-arylacetamides (8a-g). On heating of compounds 8a-e in ethanol containing anhydrous sodium carbonate, they converted into 7-acetyl-1-amino-N-aryl-5,8-dimethyl-8-hydroxy-6-(3-nitrophenyl/4-nitrophenyl)-6,7,8,9-tetrahydrothieno[2,3- c]isoquinoline-2-carboxamides 9a-e. Structural formulae of all synthesized compounds were characterized on the basis of their spectroscopic data. Also,

On the other hand, many nitro -group-conttaining compounds are reported to possess versatile applications in the elds of biochemistry and medicine [20][21][22][23].
In view of the above observations, the current work was planned to synthesize and characterize of some new 5,6,7,8-tetrahyroisoquinolines and related 6,7,8,9-tetrahyro-thieno [2,3-c]isoquinolines bearinng 3nitrophenyl or 4-nitrophenyl moiety with the hope that these new compounds will nd good applications in both biological and medicinal elds owing to their incorporation of various pharmacophores. Also, the applications of some synthesized compounds as anticancer and as antioxidant agents have been carried out and the obtained results are reported herein.

Characterizaton
The structures of newly synthesized compounds were characterized and con rmed on the basis of their spectroscopic data (cf. Experimental part). and 1651-1624 cm -1 corresponds to acetyl group and amidic carbonyl group, respectively. 1 H NMR spectra of 9a-e showed the presence of a broad singlet signal referred to the amino group at δ value ranged from 6.90 to 7.14 instead of the signal of SCH 2 group which exists in the spectra of 8a-e. The presence of tertiary alcoholic group in all compounds was acertained from their 1 H NMR spectra which possess a singlet signal at δ value ranged from 4.56 to 4.89 equivalent to one proton of (OH) group. 1 H NMR spectra of all compounds displayed characteristic signals at certain δ values which are equivalent to the protons of cyclohexene ring and in accordance with those reported before for their analogues [25]. 13  and 59.7 μM respetively, (iii) compounds 8f and 9c exhibit the highest activity and (iv) rest of the tested compounds being inactive against the two cell lines under investigation.  1% at 100 µM   Table 3 declared variable percentage of inhibition of DPPH scavenging activity of the tested compounds in a dose-dependent relationship compared with vitamin C as a standard. The highiest dose of synthesized compounds that is 0.10 µg/mL represents the highest antioxidant activity of all compounds relative to vitamin C. The synthesized compounds 2a, 2b, 4a and 9a showed the highest antioxidant activity at concentration of 0.1µg/mL (dose-dependent manner) . The DPPH scavenging activity of the most potent compounds 2a, 2b, 4a, 9a compared with that of Vitamine C in a dose dependent manner are given in Table 4. The DPPH scavenging activity of the latter compounds obeys the order 2b > 4a > 9a > 2a (Figure 3).

Experimental Section
General Melting points were determined on a Gallan-Kamp apparatus and are uncorrected. The IR spectra were recorded on a Shimadzu 470 IR-spectrophotometer (KBr; ν max in cm -1 ). The 1 H and 13 C NMR spectra were recorded on a Varian A5 500 MHz spectrometer using DMSO-d 6 (except for compounds 3 and 4a in CDCl 3 ) as a solvent and tetramethylsilane (TMS) as internal reference. Coupling constants (J values) are given in Hertz (Hz). The purity of the obtained products is checked by TLC.
The solid that formed while hot was collected, washed with water, dried in air and then crystallized from dioxane to give compounds 9a-e; yield: 80-86%.

Cytotoxic activty
The cytotoxicity activity of the some synthesized compounds was determined according to the MTT method [26-28].
The pancreatic (PACA2) and human cancer lung (A549) cells were cultured in Dulbecco's modi ed Eagle's medium supplemented with 10% fetal bovine serum and 1% GlutaMAX. Then the cells were seeded into sterile 96-well plates at a density of 10 × 10 3 cells/well and maintained at 37°C for 24 h.  Cytotoxic activity of different concentrations of compounds 9a, 9c and 9e against A549.