Synthesis and applications of (R)- and (S)-pantolactone as chiral auxiliaries

Chiral auxiliary-based reactions constitute one the most intense research areas in organic chemistry. During the last three decades (R)-pantolactone and to a minor extent its (S)-enantiomer have been used as very efficient chiral auxiliaries, thus contributing to the development of chiral auxiliary-based asymmetric synthesis as a common approach for the preparation of enantiomerically pure compounds. This review covers the syntheses of both (R)- and (S)-pantolactone, as well as their applications not only as chiral auxiliaries in asymmetric synthesis, but also in racemate resolutions and as chiral templates. The development and applications of several analogs of pantolactone with improved profile is also discussed.