Chimin Sheu

Gating as a control element in constrictive binding and guest release by hemicarcerands

Theoretical modeling of the dynamics of complexation and decomplexation of guest molecules by container molecules reveals that gating has a critical influence on the ease of formation and stability of host-guest complexes. Hosts equipped with gates can form very stable complexes with a variety of guests under readily achievable conditions. Gating involves conformational processes of the host molecule that alter the size of the portals through which guest molecules pass. “French door” and “sliding door” mechanisms of gate opening are identified.

Photooxidation of Troglitazone, a New Antidiabetic Drug *

Troglitazone (CS‐045) is a new oral antidiabetic drug reported to be effective in insulin‐resistant diabetes and to show antihypertensive effects. Photooxidation of troglitazone gave the quinone and quinone epoxide as the major final stable products. An intermediate observed by NMR spectroscopy was shown to be the hydroperoxydi‐enone, which is moderately stable at room temperature. The rate constant of singlet oxygen quenching by troglitazone is 2.14 × 108M−1s−1 and the reaction rate constant in acetone‐d, is 8.64 × 10, M−1 s−1. Only the chroman ring of troglitazone reacts with and quenches singlet oxygen significantly, and its reactivity and products are analogous to those of a‐tocopherol. The reactivity of CS‐045 toward singlet oxygen is much larger than that of the related compounds lacking the chroman ring.