Synthesis of monoprotected diamines derived from 1,5-disubstituted spiro[2.3]hexane and 5-azaspiro[2.3]hexane scaffolds is described. In both cases, the method relied on the cyclopropanation of the corresponding cyclobutane or azetidine derivatives. In the case of monoprotected 1,5-diaminospiro[2.3] hexanes, the title products were obtained as single diastereomers. X-Ray diffraction studies supported by exit vector plot (EVP) analysis showed that the obtained building blocks are promising piperidine/cycloalkane isosteres with potential utility to drug discovery. Also, conformations observed in the crystalline state for the two different diastereomers of 1,5-diaminospiro [2.3]hexane derivatives prompt their application in design of βturn and sheet-like peptidomimetics, respectively.