Acetyl thiyl

The second mechanism is due to Kozarich and co-workers [39] (Figure 11). The initial step here is the abstraction of a hydrogen atom from Cys419 by the glycyl radical, forming a transient thiyl radical. Addition of this thiyl radical to the keto group of the pyruvate results in the formation of a tetrahedral oxy-radical intermediate. This intermediate collapses into an acetylated cysteine and... 

The next step is the addition of the thiyl radical to the carbonyl carbon of pyruvate, yielding a tetrahedral oxy-radical intermediate. The calculated energy of this intermediate, relative to the free reactants, is +9.9 kcal/mol, and the barrier for its formation is calculated to 12.3 kcal/mol. The barrier for the dissociation of the radical intermediate into acetylated cysteine and formyl radical is calculated to be only 2.8 kcal/mol with an exothermicity of 3.9 kcal/mol. Taken together, the total reaction ... 

Methyl penta-A,0-acetyl-a-D-lincosaminide, related to lincomycin (55, X=OH), has been prepared from myo-inosotol/ Lincomycin has been converted by a double inversion sequence via the chloride (clindamycin) into the analogues 55, X=N3, imidazol-2-thiyl, etc/ and the lincosamine-related structure 56 has been made from l,2 3,4-diO-isopropylidene-D-galactose/ ... 

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