脱水缩合

[[N-氨甲酰天冬氨酸（N-carbamoyl aspartate，C-Asp）]]->[[二氢乳清酸]]+$

\usepackage{chemfig}
\begin{document}

\chemfig{
	(=[4.7,0.6]O)
	(-[2,0.6]NH_2)
	(-[7.3,0.6]N(-[6,0.3]H)
		-[0.7,0.6]
			(-[7.3,0.6]
				(=[6,0.6]O)
				(-[0.7,0.6]OH)
			)
			(-[2,0.6]-[3.3,0.6]
				(=[2,0.6]O)
				(-[4,0.6]HO)
			)
	)
}

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

\chemfig{
	(=[4.7,0.6]O)
	(-[2,0.6]N(-[4,0.2]H)(-[0.7,0.6]))
	(-[7.3,0.6]N(-[6,0.3]H)
		-[0.7,0.6]
			(-[7.3,0.6]
				(=[6,0.6]O)
				(-[0.7,0.6]OH)
			)
			(-[2,0.6]-[3.3,0.6]
				(=[2,0.6]O)
			)
	)
}
+$

\end{document}