Enantioselective synthesis of (S)-(+)-pantolactone
[reaction: see text] The Prins reaction of a chiral alkylidene morpholinone derived from (1R,2S)-ephedrine and 3-methyl-2-oxobutanoic acid proceeds with good diastereoselectivity to generate a spiro bis-acetal. Lewis acid mediated diastereoselective reductive cleavage of the spiro acetal and subsequent removal of the ephedrine portion generates a alpha-hydroxy-gamma-methoxy carboxamide which is readily converted to (S)-(+)-pantolactone with high enantiomeric excess.
Pansare
SV
Division of Organic Chemistry (Synthesis), National Chemical Laboratory, Maharashtra, India. pansare@ems.ncl.res.in
Jain
RP