sentences:  In order to prevent possible metabolic deactivation, several refinements such as methylation on the C alfa of the benzyl ring and fluorination on the phenyl ring were introduced.These changes produced the compound MK-869, which showed high affinity for the NK1 receptor and high oral activity (figure 3).MK-869 is also called aprepitant, and was studied in pain, migraines, emesis and psychiatric disorders.