The nose is a sensitive chemical detector able to register a wide variety of low molecular weight hydrophobic compounds, or odorants. The sense of smell begins with the molecular recognition of the odorants by G-protein coupled receptors (GPCRs) expressed in the cellular membrane of olfactory neurons. The human genome encodes almost 400 different GPCRs but little is known about the recognition strategies they employ to detect, and discriminate among, detectable odorants. The difficulty in obtaining structural data on the membrane-bound GPCR-odorant interactions has prompted us to make novel probes designed to understand the binding preferences of a representative olfactory receptor, the rat OR-I7, whose natural ligand was previously found to be octanal. We will present the design, synthesis and initial testing of a series of conformationally restricted octanal analogs, each containing eight carbons but constrained in various ways. These compounds are designed to reveal the shape requirements of OR-I7, and to enable us to understand which octanal carbon-carbon bonds must remain freely rotatable in order to be recognized by OR-I7.