Background:The small subunit of quinohemoprotein amine dehydrogenase contains three Cys-to-Asp/Glu thioether bonds. Results:The radical S-adenosyl-L-methionine (SAM) enzyme QhpD catalyzes the single-turnover reaction of thioether bond formation in the protein substrate. Conclusion:The thioether bond formation by QhpD proceeds sequentially in an N-to C-terminal direction of the polypeptide. Significance: Our findings uncover another challenging reaction of radical SAM superfamily of enzymes.

Fluoride ion-induced desilylation of N,N-dimethyl-N-[(trimethylsilyl)methyl]-α-(methoxycarbonyl)-4-substituted benzylammonium salts (7) gave two Stevens rearrangement products:  methyl 3-(dimethylamino)-2-(4-substituted phenyl)propionates (13) from N-methylides 8, and methyl 3-(dimethylamino)-3-(4-substituted phenyl)propionates (15) from N-benzylides 10. Additional Stevens rearrangement products, methyl 2-(dimethylamino)-3-(4-substituted phenyl)propionates (16), were competitively formed from ylides 12 when the cesium fluoride used was not predried. The mechanism of the isomerization from methylides 8, which was initially generated, to 10 and 12 is discussed.

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