This issue of Enamine Product Focus represents a family of Building Blocks possessing sulfone moiety as a part of a cyclic unit. All the building blocks processing cyclic sulfone moiety have some common features that make the design of potential drug candidates particularly efficient.

A concept of bioisosterism has attracted much attention in recent years. The success of this strategy in developing new substances which are therapeutically attractive has observed a significant growth in distinct therapeutic classes, being amply used to discover new analogs of commercially attractive therapeutic innovations, and also as a tool useful in the molecular modification.

A lead compound with a desired pharmacological activity may have undesirable characteristics that limit its bioavailability, or structural features which adversely influence its metabolism and excretion from the body. Bioisosterism represents one of the approaches used by the medicinal chemists for rational modification of lead compounds into safer and more clinically effective agents.

This issue of Enamine Product Focus represents a family of Building Blocks containing Hydrazine unit. Several aspects of utilizing the hydrazine building blocks for the design of potential drug candidates can be outlined. Despite hydrazines themselves are rarely thought as promising drug candidates, some successful examples of drugs possessing hydrazine moiety can be found, e. g. antiparkinsonic agent Carbidopa (Lodosyn®), antidepressant Phenelzine (Nardil®) or vasodilator Hydralazine (Apresoline®).

The synthesis of functional organic compounds for different applications largely relies on laborious approaches involving an extensive usage of protecting groups. Nowadays chemoselective routes to the construction of complex molecules are becoming a good alternative because they shorten the length of multistep syntheses by excluding protecting groups and, as a consequence, lead to increased overall yields.