Synthesis of 2-imino and 2-hydrazono thiazolo[4,5-d]pyrimidines as corticotropin releasing factor (CRF) antagonists

Corticotropin-releasing factor (CRF) is an important neuropeptide hormone which controls the body's overall response to stress. It plays a crucial role in regulating the behavioral, cardiovascular, immune and gastrointestinal systems. Over-activation of the CRF system has been implicated in many disorders including anxiety, depression, drug addiction, hypertension, Irritable Bowel Syndrome (IBS), peptic ulcers, inflammation and others. Thus, binding of CRF to its receptors is an attractive target to develop new medications which aim at treating ailments associated with chronic stress. Numerous small-molecule non-peptide CRF receptor antagonists were developed and many are in various stages in clinical trials. Many showed great promise in treatment of anxiety, depression, peptic ulcers, inflammation, IBS and drug addiction. In our recent previous work, the development of two series of pyrimidine and fused pyrimidine CRF antagonists were described. In continuation of our efforts in this direction, in the current manuscript, the synthesis of a third series of CRF receptor antagonists is described. The binding affinities of select compounds for the type 1 receptor of CRF (CRF₁R) were determined and compared to a standard CRF antagonist drug antalarmin. A lead compound was identified and further evaluated by measuring its effect on the inhibition of the agonist-stimulated accumulation of second messengers.