Design, synthesis and spectral studies of novel bile acid-arene conjugates: Trans to cis isomerization of azobenzene core controlled by bile acid hydrophobicity

Four bile acid-arene conjugates, 1,4-bis[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene dibromide (1), 1,3,5-tris[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene tribromide (2), bis{4-[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide (3), and bis{4-[dimethyl(3α-hydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide (4), have been synthesized in good yields, and their structures have been characterized by 1H, 13C, 13C DEPT-135, PFG 1H, 13C HMQC, PFG 1H, 13C HMBC, and PFG 1H, 15N HMBC NMR spectra. Their molecular weights and elemental compositions have been determined by ESI-TOF mass spectrometry and elemental analyses. Trans to cis isomerization of azobenzene derivatives 3 and 4 have also been studied. It was found that by increasing the hydrophobicity of bile acid moiety (from cholyl to lithocholyl) the trans to cis photoinduced isomerization tendency is increased in a protic solvent.