The boronic acid functional group is known to bind compounds with the diol group tightly and reversibly in aqueous environment and has been used as a recognition moiety for the design of carbohydrate sensors. The first chapter of the dissertation studies the synthesis and substitution effect on the affinity and selectivity of a known boronic acid-based glucose sensor. In such a sensor design effort, the availability of a signaling event, whether it is fluorescence or UV, is crucial. The second chapter studies the detailed mechanism on how a well-known fluorescent boronic acid compound changes fluorescent properties upon binding. A new mechanism has been established which corrected a decade old mistake. In the third chapter, a series of boronic acid-based sensors were designed and synthesized for sialic acid, which is part of tetrasaccharide found on many cell surface carbohydrates. Such sialic acid sensors could be very useful for the development of new type of anti-influenza therapy. The fourth is on the design and synthesis novel and selective inhibitors for phosphodiesterase 4 (PDE4), which are potential anti-asthma agents.