Gates's
total synthesis of
morphine was the first of its kind and an important confirmation of the structural determination made by
Robert Robinson some 27 years prior. The synthesis was based on the construction of a cyanodiketone from the
dihydroxynaphthalene shown below. The key step was a high-pressure
Diels-Alder reaction with
butadiene that established the fused ring system core. Reductive coupling between the
hydroxyl and
cyano groups furnished the ethylamine bridge and further elaboration (including an arduous epimerization of the highlighted
stereocenter) established the so-called "Gates Intermediate." Syntheses published thereafter focused, for a time, on improvements to the synthesis of this intermediate as well as the final steps. ==References==