Pseudomerucathine

The synthesis of merucathinone described above followed a procedure that was also utilized for the synthesis of two other khat constituents, merucathine and pseudomerucathine (408). The ethyl carbamate of L-alanine l(S)-15] was de-protonated with 2 equiv butyllithium and subsequently reacted with 1 equiv styryllithium to yield the ester (5)-16. Reduction of (S)-16 with diisobutylalumi-num hydride gave a 1 1 diastereomeric mixture of (1S,2S)-17 and (1S,2R)-17. Treatment of this diasteromeric mixture with 1 M potassium hydroxide in methanol at room temperature for 4 hr resulted in the formation of the epimeric oxazolidines (4S,5/ )-18 and (4S,5S)-18 in high yield. These epimers could easily be separated quantitatively by flash chromatography. Ring opening of epimers 18 was accomplished by treatment with potassium hydroxide in methanol-water under reflux. 

The fresh leaves of the khat shrub (Catha edulis) are chewed by several millions of people in East Africa and the Arabian peninsula for their euphoric and stimulating properties (284). The rather newly discovered alkaloid cathinone [(S)-a-aminopropiophenone] is responsible for the stimulating properties of khat (284). It has been shown that cathinone induces release at physiological catecholamine storage sites in a manner similar to that of amphetamine. Further results suggest that cathinone and amphetamine produce their stimulant effects via the same dopaminergic mechanism (599). The more recently discovered khat constituents merucathinone, merucathine, and pseudomerucathine were found to have only weak dopamine-releasing effects and were therefore considered unlikely to play an important role in the stimulatory actions of khat leaves (414). 

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