SYNTHESIS AND STRUCTURAL INVESTIGATION OF 2 POTENTIAL BORONATE AFFINITY-CHROMATOGRAPHY LIGANDS CATECHOL [2-(DIISOPROPYLAMINO) CARBONYL]PHENYLBORONATE AND CATECHOL [2-(DIETHYLAMINO)CARBONYL, 4-METHYL]PHENYLBORONATE

Two potential boronate affinity chromatography ligands, catechol [2-(diisopropylamino)carbonyl]phenylboronate (I) and catechol [2-(diethylamino)carbonyl,4-methyl]phenylboronate (II) were synthesized by directed ortholithiation followed by boronation. Single crystal X-ray analyses of compounds I and II demonstrated an internal coordination bond between the boron atom and the carbonyl oxygen atom, rendering the boron atom environment to;be tetrahedral. In addition, B-11 NMR data also indicated that the boron environment is tetrahedral. The coordinated carbonyl oxygen-B bond length is 1.556(9) Angstrom compared to an average B-O bond length of 1.47 Angstrom to the catechol ligand. They are ideal models of a new type of ligands to study boronate affinity chromatography because they may esterify with catechols at neutral pH conditions.