Substituted ethyl 5-oxohomoadamantane-4-carboxylates were subjected to reactions with several nucleophiles to establish some aspects of the carbonyl reactivity. However, only one example of the desired Claisen retro-reaction was observed as 3,7-disubstituted bicyclo[3.3.1]nonane formation. Most of the reactions yielded α-substituted homoadamantan-5-ones or some products of their further transformations. Reductive amination of substituted homoadamantane-5-ones gave several homoadamantane-fused nitrogen heterocycles, which could be considered as GABA- and/or ∂-aminovaleric acid analogues. Reduction products of several substituted ketones were observed as single products when treated with organomagnesium reagents. These deviations from the general chemical reactivity patterns are associated with steric factors and the geometry of the cage unit and could be a particular case, which is reflecting the overall specificity of the chemistry of cage carbonyl compounds.