Cycloalkylcarboxylic acids

Relatively inaccessible cycloalkylcarboxylic acids can be produced via these Favorskii rearrangements (for example equation 7), and they have been especially useful for the introduction of alkyl groups at C-17 of the steroid nucleus. Thus the pregnenolones (10) and (11) can be converted into mixtures of rearrangement products (12) and (13), with the latter usually predominating in polar, protic solvents (Scheme... 

Starting with (S)- or (7 )-l nonproteinogenic x-amino-a-cycloalkylcarboxylic acids and heterocyclic x-amino acids are also obtained with high enantiomeric purity110. 

---