1-2-3-4-5-6成环（ATIC(E2)）

[[5-甲酰胺基咪唑-4-氨甲酰核苷酸（FAICAR）]]->[[IMP：肌苷酸，次黄嘌呤核苷酸]]+$

\usepackage{chemfig}
\begin{document}

\chemfig{
	\fbox{R}-[2,0.8]N(-[2,0.25]9)
	-[3.5,0.6](-[3.3,0.25]4)(-[4.5,0.7]N(-[2,0.25]3)=[3.3,0.6](-[5,0.25]2))
	=[2,0.8](-[4.8,0.25]5)(-[3,0.7](=[2,0.7]O)
	(
		-[4.7,0.8]N(-[2,0.3]1)
		-[4,0.3]H_2
	)
	(-[6,0.25]6))
	-[0.5,0.8]N(-[5.5,0.25]7)(-[,0.3]H)
	=[6.55,0.8]
		(-[4,0.2]8)
		-[5.25,0.6]
}

\begin{tikzpicture} 
\draw [->] (0,0) to node[above] {ATIC(E2)} (1,0); 
\end{tikzpicture}

\chemfig{
N(-[7.3,0.25]1)
-[6,0.8](-[.7,0.25]2)
=[7.3,0.8]N(-[2,0.25]3)
-[0.8,0.8](-[3.3,0.25]4)
=[2,0.8](-[4.8,0.25]5)
	(
		-[0.5,0.8]N(-[5.5,0.25]7)
		=[6.55,0.8](-[4,0.25]8)
		-[5.25,0.8]N(-[2,0.25]9)(-[6,0.8]\fbox{R})
		-[3.5,0.6]
	)
-[3.3,0.8](-[6,0.25]6)(=[2,0.8]O)
-[4.8,0.6]
}

+$

\end{document}