A NOVEL SUGAR SENSING SYSTEM DESIGNED WITH A COOPERATIVE ACTION OF A BORONIC-ACID-APPENDED ZINC PORPHYRIN AND A 3-PYRIDYLBORONIC ACID AXIALLIGAND

The cooperative action of two boronic acids is indispensable to the se lective binding of saccharides in aqueous solution and the binding pro cess can be spectrophotometrically monitored by using porphyrins as a chromophoric probe. It is nor so easy, however, to synthesize porphyri ns that satisfy these prerequisites, i.e., porphyrins bearing two appr opriately-arranged boronic acid groups within a molecule. In this pape r, we report that such a diboronic-acid-based porphyrin receptor can b e easily designed by utilizing the self-assembling nature of a Zn(II) porphyrin and an axial ligand: That is, a mixture of boronic-acid-appe nded Zn(II) porphyrin (1-Zn) and 3-pyridylboronic acid (2) self-organi zes to create a novel diboronic acid system for saccharide (S) recogni tion. Thus, the P-Zn 2 S ternary complexes give the CD spectral patter n inherent to saccharide absolute configuration. The present study is a new example for sugar sensing using a boronic acid-porphyrin self-as sembly.