TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises: either reacting substituted 1-(3,6-dihydro-2H-pyridin-1-yl)prop-2-en-1-one compounds of formula (A) with substituted 3-bromopyridine compounds of formula (B) by heck reaction in a solvent in the presence of a palladium catalyst, ligand and a base; or reacting substituted 1,2,3,6-tetrahydropyridine compounds of formula (C) with pyridine compounds of formula (D) by acid amine coupling in a solvent in the presence of a coupling reagent and a base. Preferred Components: In the heck reaction: the solvent comprises polar solvents including N,N-dimethylformamide (DMF), propionitrile, acetonitrile, tetrahydrofuran (THF)s or dimethylsulfoxide (DMSO); the palladium catalyst comprises 1,1-bis(diphenylphosphino) ferrocene dichloropalladium(II), tetrakis(triphenylphosphine)palladium(0), tris(dibenzylideneacetone)dipalladium(0) or palladium(II) acetate; and the ligand comprises tri(o-tolyl)phosphine, tri(m-tolyl)phosphine or tri(p-tolyl)phosphine. In the acid amine coupling reaction: the solvent is DMF, THF, DMSO or dichloromethane; the coupling reagents is benzotriazole-containing coupling reagent such as 1-hydroxybenzotriazole, benzotriazole-1-yloxytris(dimethylamino)phosphoniumhexafluorophosphate or 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate; azabenzotriazole containing reagent is O-(7-azabenzotriazole-1-yl)-N or dicarboimides containing reagent such as 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, dicyclohexylcarbodiimide or 2-(7-aza-1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate; and the base is triethylamine, or N,N-diisopropylethylamine. Preferred Definitions:    X = N; and    R1 = H.    ACTIVITY - Antibacterial. The antibacterial activity of (I) was tested against Staphylococcus aureus. The result showed that (E)-6'-(3-oxo-3-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-1-en-1-yl)-1'H-spiro(cyclopropanel-1,3'-(1,8)naphthyridin)-2'(4'H)-one exhibited an IC50 value of less than or equal to 0.4 ~mM.    MECHANISM OF ACTION - Enoyl-acyl-carrier-protein reductase inhibitor.    ADMINISTRATION - Administration of (I) is 0.001-100 mg/kg, preferably 1-10 mg/kg, orally, buccally, sublingually, rectally, nasally, topically, transdermally, vaginally or parenterally (including subcutaneously, intramuscularly, intravenously or intradermally).    SPECIFIC COMPOUNDS - 42 Compounds (I) are specifically claimed, e.g. (E)-tert-butyl 2-oxo-6-(3-oxo-3-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-1-en-1-yl)-2,4-dihydro-1H-spiro((1,8)naphthyridine-3,4'-piperidine)-1'-carboxylate of formula (Ia), (E)-6'-(3-oxo-3-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-1-en-1-yl)-1'H-spiro(cyclopropanel-1,3'-(1,8)naphthyridin)-2'(4'H)-one, (E)-6'-(3-oxo-3-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-1-en-1-yl)-1'H-spiro (cyclobutane-1,3'-(1,8)naphthyridin)-2'(4'H)-one, (E)-6'-(3-oxo-3-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-1-en-1-yl)-1'H-spiro(cyclohexane-1,3'-(1,8)naphthyridin)-2'(4'H)-one and (E)-6'-(3-oxo-3-(4-(thiophen-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-1-en-1-yl)-1'H-spiro(cyclohexane-1,3'-(1,8)naphthyridin)-2'(4'H)-one.    EXAMPLE - 0.55 ml of N,N-Diisopropylethylamine was added to a stirred solution of 350 mg of 1-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl)prop-2-en-1-one and 500 mg of tert-butyl 6-bromo-2-oxo-2,4-dihydro-1H-spiro((1,8)naphthyridine-3,4'-piperidine)-1'-carboxylate in 4 ml of DMF/16 m of propionitrile at 20-35 degrees C, and the mixture was degassed with nitrogen for 10 minutes. Then 28 mg of palladium(II) acetate and 77 mg of tri(o-tolyl)phosphine were added, again degassed with nitrogen for another 10 minutes and heated at 110 degrees C for 16 hours. The reaction mixture was cooled to 20-35?oC and filtered through Celite (RTM: Diatomaceous earth filter aid). The filtrate was rotary evaporated under vacuum to get residue, which was purified by column chromatography using mixture of 3% of methanol/dichloromethane as an eluent to get 150 mg of (E)-tert-butyl 2-oxo-6-(3-oxo-3-(4-(thiazol-2-ylmethyl)-5,6-dihydropyridin-1(2H)-yl) prop-1-en-1-yl)-2,4-dihydro-1H-spiro((1,8)naphthyridine-3,4'-piperidine)-1'-carboxylate as a light yellow solid.