# Design, Synthesis and Antifungal Activity of Novel Benzoylcarbamates Bearing a Pyridine Moiety
## 3 Results and Discussion  
### Chemistry  
Target compounds **4a-4j** were synthesized according to the method depicted in Scheme 1. The starting material, 3-methylpyridine lost a proton under the catalysis of lithium diisopropylamide (LDA) and gave 3-pyridylmethyl lithium, followed by the treatment with ethyl 3,3-dimethylpropionate to yield 3,3-Dimethyl-1-(pyridin-3-yl)butan-2-one (**1**). Then, **1** was reduced by sodium borohydride to provide the key intermediate 3,3-dimethyl-1-(pyridin-3-yl)butan-2-ol (**2**). Finally, **2** reacted with freshly prepared substituted benzoyl isocyanate (**3**) in anhydrous tetrahydrofuran to yield the substituted benzoylcarbamate (**4**).  
Target compounds were identified by \({}^{1}\)H NMR, \({}^{13}\)C NMR, IR, and elemental analysis. In \({}^{1}\)H NMR spectra, the singlet of methyl protons of \(t\)-butyl moiety was observed at \(\delta\) 1.02-1.07 ppm. The \(\,\)methine proton can form an ABX system with its two neighboring methylene protons, thus its signal was split into a quartet around \(\delta\) 5.0 ppm, while the signals of methylene protons were split into two groups of multiplet near \(\delta\) 2.80 and 2.98 ppm, respectively. A broad peak in the range of \(\delta\) 7.90 to 9.40 ppm was ascribed to the presence of the NH proton. The signals of protons of pyridinyl and benzyl rings appeared in the range of \(\delta\) 6.86-8.45 ppm. In \({}^{13}\)C NMR spectra, the signal for the carbonyl carbon of benzoyl was observed at \(\delta\) 164.38 to 166.32 ppm, whereas that of carbamate occurred at around \(\delta\) 151.00 \(\,\)ppm. The peak at \(\delta\) 82.91-83.47 ppm corresponded to the methine carbon, whereas the peak near \(\delta\) 35.00 ppm corresponded to the methylene carbon. The signal of the methyl carbon of \(t\)-butyl was observed at \(\delta\) 25.90-26.19 ppm. In their IR spectra, the absorption peak around 3250 cm\({}^{-1}\) could be assigned to the N-H stretching vibration; the strong absorption peaks of carbamate and benzoyl  
\begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Compd.**} & \multirow{2}{*}{**R**} & \multicolumn{2}{c}{**EC\({}_{50}\) (\(\mu\)g/mL), 95\% CL**} \\ \cline{3-4}  & & \multicolumn{1}{c}{_S. sclerootomy_} & \multicolumn{1}{c}{_B. cinerea_} \\ \hline
**4a** & H & 12.67 (8.98–17.89) & 13.03 (12.02–14.11) \\ \hline
**4b** & 2-CH\({}_{3}\) & 14.96 (10.42–19.48) & 10.50 (8.49–14.03) \\
**4c** & 3-CH\({}_{3}\) & 15.89 (13.19–19.40) & 8.04 (6.54–11.68) \\
**4d** & 4-CH\({}_{3}\) & 13.18 (9.06–18.21) & 6.70 (4.03–11.02) \\
**4e** & 2-OCH\({}_{3}\) & 14.06 (10.82–19.74) & 7.84 (5.50–10.90) \\
**4f** & 2-CI & 11.84 (8.04–17.90) & 6.98 (6.24–7.79) \\
**4g** & 3-CI & 12.41 (8.19–18.80) & 6.81 (5.39–9.60) \\
**4h** & 4-CI & 10.85 (6.57–17.92) & 6.45 (5.44–7.65) \\
**4i** & 2-Br & 12.98 (9.26–16.64) & 9.80 (6.48–13.16) \\
**4j** & 4-Br & 11.25 (7.40–17.78) & 7.95 (5.21–12.15) \\ Diethofencarb & & 2.95 (1.24–5.08) & 4.72 (2.49–7.15) \\ Chlorothalonil & & 9.97 (7.51–13.22) & 6.56 (4.95–9.70) \\ Carbendazim & 0.24 (0.20–0.28) & 19.20 (13.27–27.89) \\ \hline EC\({}_{50}\): Concentration resulting in a 50% inhibition; 95% CL: 95% confidence interval of EC\({}_{50}\). \\ \end{tabular}
\end{table}
Table 1: Antifungal activities of compounds **4a–4j** (EC\({}_{50}\)).  
C=O were observed at 1740-1776 cm\({}^{-1}\) and 1679-1702 cm\({}^{-1}\), respectively. The bending vibration of _tert_-butyl displayed two peaks near 1390 and 1365 cm\({}^{-1}\)[24].