## 3 Synthetic Coumarin Derivatives in Plant Protection  
Since naturally occurring coumarins have shown biological and allelopathic potential in various organisms, their structural core is widely used as a scaffold in agricultural chemicals. Thus, osthol (7-methoxy-8-prenylcoumarin) (Figure 6), is a natural coumarin and lead compound that has been developed into commercial fungicides Osthol EW in China which exhibits effective activity against _Magnaporthe oryzae_, _Sphaerotheca fuliginea_, _Fusarium graminearum_, and _Sphaerotheca fuliginea_[32]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Phylum/** & **Species** & **Group of Coumarins** & **Specific Compounds** & \
\begin{tabular}{c} **Known Biological** \\ **Activities** \\ \end{tabular} & **Ref.** \\ \hline _Angelica pubeccns_ Maxim. _f. biserrita_ [PERSON] & simple, dihidrofuranacoumarin, & osthole, columbianadin & nematicidal & [98] \\  & _f._uranacoumarin & bergapten, xanthotoxin & nematicidal & [115] \\  & _Pleurospernum trivulomrum_ & bicouumarin & rivulobirins & unknown & [115] \\  & _Oppanax hisplugus_(Friv). & dihydrofuranacoumarin & 3′-isobutyryl-3′- & unknown & [102] \\  & Griseb. & simple, & officialin, oreoselon, & & \\  & _Pueucdamum_ sp. & simple, & ostrutin, osthol; & & \\  & & furanacoumarin & isoimperatorin & insecticidal & [93] \\  & & dihydrofuranacoumarin & xanthain, peuenarin & insecticidal & [93] \\  & _Semenovia trussiliensis_ & furanacoumarin & hhematoin, columbianadin & insecticidal & [31] \\  & _Heracleum canalicans Wall._ & uranacoumarin & 8-geranyloxy psolaren, & nematicidal & [94] \\  & _Meliottos officinalis_ & simple &
\begin{tabular}{c} dihydroumarin \\ dicouumarin \\ \end{tabular} & cytotoxicity & [24] \\  & _Mucuna birdacoaliana_ & phenylcournarin & mucolanin A & unknown & [107] \\  & _Sphanestylis margitan_ & phenylcumarin & splenostylisin A & anticancer & [68] \\  & _Pteocarpus souzuki_ & phenylcournarin & pterosonins & anticancer & [106] \\  & _Milettia thontinigii_ & pyranacoumarin, & robustic acid, & & \\  & _Solanaceae_ & _Nicotiana tabacum_ & simple & scopolin, scopoletin & antiviral & [79] \\  & _Emailaceae_ & _Baikal skillcap_ & simple & methylcumarin & antibacterial & [17] \\  & _Arabidopsis thaliana_ & simple & scopoletin & antifungal & [78] \\  & _Moraceae_ & _Ficus arciraz_ & furocomarin & bergapten, psoral & nematicidal & [95] \\  & _Dysorulph parasitic_ & bicouarnin & bidysoxyletine & unknown & [114] \\  & ([PERSON]) Kostern & simple, furocomarin & umbelliferone, & & \\  & _Tripbasti rigglia_ & simple, furocomarin & isospinpinellin, & unknown & [113] \\  & _Xantharyum entertainment_ & dihydrofuranacoumarin & xanthord & antifungal & [103] \\  & _Stuantinkus perfontus_ & Pyranocoumarin & xanthyletin & phytotoxic & [110] \\  & _Ruta angusifolia_ & dihydrofuran- & chalepensin, chalepin & anticancer, & \\  & _Clusen amisata_ & pvaracoumarin & seselin & antifeadant & [112] \\  & _Wikströmita indica_ (L) & bicouarnin & daphnoretin & antiviral, antitumor & [29] \\  & Calophyllaceae & _Mumnea longifolia_ & simple & surangib B & antifungal & [80] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: \(Cont.\)  
Figure 6: Structures of synthetic coumarin derivatives with antifungal activity. Synthetic coumarins are strong antifungal agents. Several coumarin-3-carboxamides/ hydrazides have been shown to have antifungal activities against _Botrytis cinerea_, _Colletotrichum capsaicin_, _Rhizzoctorzia solani_, _Cucumber anthrax_, and _Alternaria cucumerina_ leaf spot [117]. These compounds exhibited equivalent antifungal activity to broad-spectrum carboximide fungicides Boscalid, against _Botrytis cinerea_. For example, compound 2-oxo-2\(H\)-chrome-3-carboxylic acid \(N\)-(2-chloro-phenyl)-hydrazide (Figure 6), exhibited much more effective activity (1.80 \(\upmu\)g/mL) than the Boscalid (2.98 \(\upmu\)g/mL) against _Rhizzoctorzia solani_.