Final answer:
The provided information does not specify a developed country that has become a leading producer and distributor of synthetic drugs like XTC. References to historical and current drug trade issues show global patterns but do not pinpoint a particular country for synthetic drug production.
Step-by-step explanation:
The question seems to intertwine with multiple subjects, such as the global drug trade, economics, and international affairs. However, the information provided does not directly indicate which developed country has become a leading producer and distributor of synthetic drugs, especially XTC (ecstasy). Nevertheless, the references to opioid production and shifts in the drug market due to law enforcement and the historical context of opium trade hint towards broader patterns in drug production and distribution globally.
Several passages detail the historical context of drug trade involving opium in China and the repercussions of such a trade. Also, a transition in the United States from prescription pain pills to illicit opioids suggests a shift in the drug market affected by price and availability. However, there is no mention in the provided information about a specific developed country that is a leading producer and distributor of synthetic drugs like XTC.
It is crucial when analyzing the global drug trade to address how market pressures, legal interventions, and historical drug use patterns influence current drug distribution trends. Although specific countries have been implicated in the production and distribution of various types of drugs historically, identifying a leading developed country for synthetic drugs without current and specific data can be challenging and would require further information beyond what is provided here.