Symmetrical and inherently chiral water-soluble calix[4]arenes bearing dihydroxyphosphoryl groups

Abstract

A series of symmetrical and inherently chiral water-soluble calix[4]arenes bearing one, two or four proton-ionisable dihydroxyphosphoryl groups at the narrow rim of the macrocycle has been synthesised by consecutive treatment of appropriate diethoxyphosphoryl derivatives with bromotrimethylsilane and methanol. The calix[4]arene phosphoric acids synthesised possess pK_a-values 2.85–3.10 (CH₃OH–H₂O 70 : 30) and form salts with L-(−)-α-phenylethylamine or (1S,2R)-(+)-ephedrine in methanol solution. The salts of the inherently chiral calixarene phosphoric acids with chiral amines are easily separated into diastereomeric forms by the RP HPLC method on Separon SGX C18 or Partisil 5 ODS 3 achiral columns.