Synthesis of meta- and paracyclophanes containing unsaturated amino acid residues

Abstract [7.7], [8.8], [9.9] and [13.13] Para cyclophanes and [9.9] and [13.13] meta cyclophanes containing two unsaturated amino acid residues have been synthesised. An X-ray crystallographic study of three of the para cyclophanes and molecular modelling of two para cyclophanes and two meta cyclophanes revealed two main structural types. The ‘staggered’ structure appears to be favoured by longer hydrocarbon chains, whilst the ‘barrel’ structure appears to be more accessible to compounds containing shorter hydrocarbon chains. The [9.9] para cyclophane has been hydrogenated and deprotected to give a saturated amino acid, and an alternative approach to key aldehydes is reported.