In organic chemistry a lot of research effort is spent in creating small easy to make molecules for the sole purpose of creating larger molecules. Chemical libraries are filled this way that can eventually lead to new drugs.
As a representative of the kind of research it involves Denisenko et al. in Organic Letters (DOI) published the synthesis of a fairly small C₇H₁₁NO compound thus far overlooked. The reactants are commercially available cyclobutanone 1 and not so commercially available N,N-bis(methoxymethyl)benzylamine 2 in a double Mannich reaction with reagent trimethylsilylchloride. In the second step TFA converts the ketal group in 3 to the ketone 4.

The exact same procedure but with other cyclic ketones was already pioneered by McLeod in 2006 (DOI). The accompanying patent covers a large batch of cyclic ketones but for some reason not the C4 ones , an omission Denisenko has now successfully exploited.