Keto pantolactone hydrogenation

Roche [54] described a very efficient hydrogenation of keto pantolactone, an intermediate for pantothenic acid, carried out on multi-100-kg scale also using a Rh/bpm complex (Scheme 19). Success factors were the careful ligand fine tuning and the selection of the right anion which had an unusually strong effect both oti enantioselectivity and catalytic activity. 

Brunner et al. [43] investigated the hydrogenation of (Z)-a-A-acetamidocinnamic acid and keto-pantolactone with complexes 30 and 31 (Figure 22.13, Scheme 22.3). In 30 the planar chirality of... 

FIGURE 22.13 Rhodium complexes investigated in the hydrogenation of acetamidocinnamic acid and keto-pantolactone. 

Dimethyloxolane-2,3-dione (ketopantolactone), which contains an activated keto group, is one of the standard substrates for the enantioselective hydrogenation of carbonyl groups. Its hydrogenation product, 3-hydroxy-4.4-dimethyloxolan-2-one (pantolactone). is a precursor of pantothenic acid, a vitamin B block constituent. 

Japanese authors reported on the synthesis of (R)(-)-pantolactone (a precursor of pantothenic acid, which is an important constituent of coenzyme A) by hydrogenation of a-keto-/8,j8-dimethyl-y-butyrolactone with rhodium catalysts containing different chiral pyrrolidinediphosphines... 

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