By protecting the ketone group as an acetal, however, the problem can be circumvented. Like other ethers, acetals are unreactive to bases, hydride reducing agents, Grignard reagents, and catalytic reducing conditions. Thus, we can accomplish the selective reduction of the ester group in ethyl 4-oxopentanoate by first converting the ketone group to an acetal, then reducting the ester with LiAlH4, and then removing the acetal by treatment with aqueous acid.