04 (s, 3H, Gemcitabine molecular weight CH3), 3.69 (d, 5H, OC2H5), 5.64 (s, 1H, CH), 6.51 (d, 2H, ArH), 7.53–7.67 (m, 4H, ArH), 8.57 (s, 1H, NH), 9.46 (s, 1H, NH), 9.75 (s, 1H, OH), 9.87 (s, 1H, NH). MS (m/z): M+ calculated 472.03, found 471.08. Antimycobacterial activity was performed following a protocol previously reported.17 Compounds (7a–k) were preliminarily

assayed against to freshly isolated clinical strains, Mycobacterium furtuitum CA10 and Mycobacterium tuberculosis B814, according to the dilution method in agar. Growth media were Mueller–Hilton (Difco) containing 10% of OADC (oleic acid, albumin and dextrose complex) for M. furtuitum and Middle brook 7H11 agar (Difco) with 10% of OADC for M. tuberculosis. Substances were tested at single dose of 100 μg/mL. The active compounds were then assayed for inhibitory activity against a panel of mycobacterial (M. tuberculosis CIP 103471, M. tuberculosis H37Rv ATCC 27294) in Middle brook 7H11 agar by a standard twofold dilution method. Plates were incubated at 37 °C for 3 or 28 days. Pyrazinamide was used as reference compound because dihydropyrimidine nucleus structurally related to pyrimine nucleus of drug. After cultivation, MICs were read as minimal concentrations of drugs completely inhibiting visible of mycobacterial growth ( Table 1). A series

of 11 novel 3, 5-dichloro-2-ethoxy-6-fluoropyridin-4-amine cyclocondensed dihydropyrimidines of biological interest were synthesized and evaluated BAY 73-4506 in vitro for antimycobacterial activity, all the compounds were characterized by IR, 1H NMR, MS for their structures. Biginelli 3, 4-dihydropyrimidines, (7a–k) were synthesized relatively easily by using PTSA as an efficient catalyst compared with anhydrous

AlCl3 or HCl. The present protocol best describes the synthesis of Biginelli dihydropyrimidines. All the reported Biginelli dihydropyrimidines compounds were found to be novel and not reported elsewhere. Analyzing the activities of the synthesized compounds, the following structure activity relationships (SARs) were obtained. The fifth position of dihydropyrimidines contain 3, 5-dichloro-2-ethoxy-6-fluoropyridin-4-aminocarbonyl group contributed toward antimycobacterial and forth positions of dihydropyrimidines contain substituent like aromatic or hetero aromatic ring responsible antimycobacterial potency.7, 8 and 9 When compare with phenyl many ring substituted phenyl ring showed potent antimycobacterial activity. Substituted atom or group of atom should be strong electron withdrawing nature for potent activity because it decreases electron density in the ring. Substitution of chloro group at third position of phenyl ring showed potent action when compare with nitro atom. Fluoride substitution at position of phenyl ring showed potent antimycobacterial action because fluoride atom is strong electro negative when compare with chloride.17 Among all the substituted phenyl ring, the activity order was F > Cl > NO2 > H.