1,3,5-TRIAMINO-1,3,5-TRIDEOXY-CIS-INOSITOL, A NEW LIGAND WITH A REMARKABLE VERSATILITY FOR METAL-IONS .2. SAFE AND EFFICIENT LIGAND PREPARATION AND STRUCTURE OF THE FREE LIGAND AND THE CO-III COMPLEX

A new, convenient, and safe route to 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) was investigated by hydrogenation of azo-coupled derivatives of phloroglucinol. In the presence of acetic anhydride, the reduction of trisphenylazophloroglucinol (H2/Pd(5%) on C) resulted in the formation of tri-, hexa-, and nona-acetylated derivatives of triaminophloroglucinol. All three compounds are air-stable, colorless solids. However, the succeeding hydrogenation to the cyclohexane derivative failed. Trisodiumtris(p-sulfonatophenylazo)phloroglucinol could be hydrogenated in a one-pot reaction to the desired taci . 1.5 H2SO4 using a Pt/Rh oxide as catalyst. taci provides two distinct chair conformations with either three amino or three hydroxy groups for metal binding. The unique metal-binding properties are discussed in terms of minimal conformational changes required for coordination. Conformational analysis, based on X-ray structural data of [BiCl6][H-3(taci)] . 2 H2O (Pnma, a = 24.314 (5) angstrom, b = 10.215 (2) angstrom, c = 7.422 (8) angstrom, R = 5.8%) and [Co(taci)2(NO3)3]. 2 H2O (C2/c, a = 22.912 (8) angstrom, b = 8.942 (2) angstrom, c = 14.731 (3) angstrom, beta = 128.66 (2)-degrees, R = 4.9%) and the previously investigated [Cr(taci)2]3+ revealed an almost ideal chair conformation in all three molecules.