This bicyclic compound consists of the fusion of benzene and pyrazole. The second nucleophile is methylmagnesium bromide expulsing the pyrazole group. Several research groups have studied six-membered ring pyrazole bioisosteres. In 1959, the first natural pyrazole, 1-pyrazolyl-alanine, was isolated from seeds of watermelons. It is one of several isomeric derivatives of pyrazole that contain two methyl substituents. Reaction with diazomethane at the conjugated double bond at 16 gives first the pyrazole (6). The 5-substituent of the pyrazole is involved in receptor recognition and antagonism. Numbering of the central pyrazole ring is shown in Figure 2. This set contains pyrrole, imidazole, pyrazole, triazoles, tetrazole, and pentazole. The first mesoionic carbenes based on pyrazole have been reported by Huynh in 2007. O3-acetyl-L-serine&colon;pyrazole 1-(2-amino-2-carboxyethyl)transferase. Notable drugs containing a pyrazole ring are celecoxib (Celebrex) and the anabolic steroid stanozolol. It can be viewed as a derivative of pyrazole possessing an additional keto (=O) group. When hydrazine hydrate is used, a pyrazole parent body is formed in 84% yield. Pyrazole is an organic compound with the formula CHNH.