Parallel kinetic resolution of tert-butyl (RS)-6-alkyl-cyclohex-1-ene-carboxylates for the asymmetric synthesis of 6-alkyl-substituted cishexacin derivatives

Excellent levels of enantiorecognition are displayed by tert-butyl (RS)-6-n-alkyl-cyclohex-1-ene-carboxylates in mutual kinetic resolutions with lithium (RS)-N-benzyl-N-(α-methylbenzyl)amide. Therefore a 50:50 pseudoenantiomeric mixture of lithium (S)-N-benzyl-N-(α-methylbenzyl)amide and lithium (R)-N-3,4-dimethoxybenzyl-N-(α-methylbenzyl)amide allows their efficient parallel kinetic resolution, affording differentially protected 6-n-alkyl-cishexacin derivatives in high yield and >95% de. N-Debenzylation and ester hydrolysis give access to the corresponding homochiral 6-n-alkyl-substituted cishexacin derivatives. © 2008 Elsevier Ltd. All rights reserved.