Oxidative coupling of 3-(3-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester (2) gave dimethyl 3, 3′-(5, 5′-di-tert-butyl-6, 6′-dihydroxybiphenyl-3, 3′-diyl)-dipropionate (1c), which upon phosphorylation/transesterification with a phosphochloridite derived from (R)- binaphthol, formed the new unsymmetrical binaphthol-bridged diphosphite 4. A rhodium catalyst based on 4 as ligand gave predominantly iso-selectivity in the hydroformylation of ...