Contributions of the international symposium on macrocyclic chemistry to the development of macrocyclic chemistry

Abstract

In the early 1960s, Charles J. Pedersen at du Pont serendipitously discovered the compound that later came to be known as dibenzo-18-crown-6 (DB18C6). He isolated DB18C6 in a 0.4% yield from a "brownish goo" while attempting to prepare a completely different compound [1]. The decision to expend the effort needed to isolate, purify, and characterize the compound that became known as DB18C6 represents a true example of scientific creativity and luck. Many organic chemists have isolated pure compounds from various shades of .,goo", but few have had the experience of seeing a new field of chemistry arise from their .,goo" as Pedersen did. Pedersen knew he was on to something important when his subsequent characterization of the colorless, crystalline by-product revealed that its solubilization in methanol was due to the presence of Na+ and that its molecular weight was double that of benzo-9-crown-3 (B9C3). Pedersen [1] remarks that with the "realization that I had something very unusual and with the utmost curiosity and anticipation, I devoted all my energies to the study of this fascinating class of ligands by synthesizing a great variety of macrocyclic polyethers and determining their interaction with inorganic cations." The culmination of this effort was the publication of a monumental paper by him in 1967 [2]. The publication of Pedersen's work attracted instant and increasing attention from a variety of scientists worldwide. During the ensuing decade, research in an increasing number of laboratories led to the synthesis and characterization of many novel macrocyclic chemical structures, and to the application of macrocycles in a wide variety of fields. This effort cut across many areas including organic and inorganic synthesis, biochemistry, ion transport in membranes, phase transfer catalysis, and structure analysis. One of the identifying characteristics of this new developing field of macrocyclic chemistry was the focus on the high selectivity that host macrocycles had for a variety of guest compounds. As the principles governing this selectivity were discovered, the intelligent design of hosts with pre-determined selectivity for specific guests became possible. During this period, terms with new meanings appeared in the chemical literature including macrocyclic chemistry, host-guest chemistry, crown compounds, molecular recognition, nanochemistry, selective cation and anion complexation, phase transfer catalysis, and supramolecular chemistry. Dr. James J. Christensen of Brigham Young University (BYU) and one of us (RMI) were two of the first scientists to visit Pedersen in his DuPont laboratory following publication of his 1967 paper [2]. Our interest at that time was in the highly selective carrier-mediated transport of K+ and Na+ in biological membranes. Pedersen's results offered the possibility of using cyclic polyethers to study selective cation transport [3]. Indeed,Pedersen's work resulted in a resurgence of interest in alkali metal ion chemistry. The ability of macrocycles, natural and synthetic, to selectively interact with these cations provided the opportunity to investigate their chemistry in ways that had not been possible before. By the late 1970s, the growth of macrocyclic chemistry was impressive and the field had attracted persons from many disciplines. © 2005 Springer. Printed in the Netherlands.