Only the R enantiomer of prozac is effective as an antidepressant
The S enantiomer of propranolol is a beta-blocker, whereas the R enantiomer has recently been discovered to act as a contraceptive (although not used as such)
Thalidomide has a useful R enantiomer, whereas the S enantiomer is a teratogen - but racemises in vivo so enantiopurity is no solution
Unsymmetrical ketones (e.g. acetophenone) have Re and Sienantiotopic faces, so reduction with NaBH4 leads to a racemic mixture of S and R alcohols, respectively (due to enantiomeric transition states, which must have equal energy)
Can make one enantiomer at a greater rate but using a chiral analogue of BH4− (transition states now diastereomeric, thus not equal in energy)
Often an unsuitable solution, as the chiral reagent can be large and expensive, and possibly only slightly enantioselective
Chiral auxiliary – a chiral molecule temporarily added to a substrate. With the auxiliary attached, the substrate undergoes a diastereoselective reaction to form mostly one of two possible diastereomers. Subsequent removal of the auxiliary leaves enantiomeric products, hopefully with one enantiomer in great excess.
Synthesised from the (S) enantiomer of the natural product pulegone
Its OH group reacts with acyl chlorides to form 8-phenylmenthyl esters
8-Phenylmenthyl acrylate esters can undergo asymmetric Diels-Alder reactions with achiral cyclopentadienes in the initial stages of the syntheses of several prostaglandins
Candida lipase with vinyl acetate will enantiospecifically acetylate one of the two OH groups in the meso compound cis-4-cyclopentene-1,3-diol (CAS # 29783-26-4)
The other enantiomer of the product can be made by acetylating both OH groups with acetic anhydride, then enantiospecifically hydrolysing one of them with Candida lipase and water