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

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