Synthèse énantiospécifique des acides (+)‐(2 R )‐ et (−)‐(2 S )‐éthyl‐6‐dihydro‐3,4‐méthyl‐2‐oxo‐4–2 H pyranecarboxylique‐5

Enantiospecific Synthesis of (+)‐(2 R )‐ and (−)‐(2 S )‐6‐Ethyl‐3,4‐dihydro‐2‐methyl‐4‐oxo‐2 H ‐pyran‐5‐carboxylic Acid The two enantiomers (−)‐(2 S )‐ and (+)‐(2 R )‐6‐ethyl‐3,4‐dihydro‐2‐methyl‐4‐oxo‐2 H ‐pyran‐5‐carboxylic acid (( S )‐ and ( R )‐ 7 ) have been synthesized from (+)‐(3 S ) and (−)‐(3 R )‐3‐hydroxybutanoates, respectively ( Scheme 1 ). By reduction and decarboxylation, the tetrahydro‐2 H ‐pyranols (2 R , 4 R , 6 S )‐ and (2 S , 4 S , 6 R )‐ 13 , respectively, were obtained with an enantiomeric excess of ≥ 93%.