The asymmetric synthesis and conformational analysis of new C2-symmetric macrocycles derived from head-to-head linked α-amino acids and benzene or pyridine

The synthesis of several novel 15-18-membered macrocycles containing 1,3-disubstituted benzene or 2,6-disubstituted pyridine in a chiral environment is described. The syntheses used a series of di(N-alpha-tosyl-L-alanylamido)alkanes, which could be prepared in good yield. The macrocyclisation reaction with 1,3-di(bromomethyl)benzene or 2,6-di(bromomethyl)pyridine was facilitated by the use of caesium carbonate as base, and NMR and molecular modelling were used to study the preferred conformations of the macrocycles. (C) 2001 Elsevier Science Ltd. All rights reserved.