CROSS-CHIRAL EXAMINATIONS OF MOLECULAR ENANTIOSELECTIVE RECOGNITION BY FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY - HOST-GUEST COMPLEXATIONS BETWEEN CHIRAL CROWN-ETHERS AND CHIRAL ORGANIC AMMONIUM-IONS

Using fast atom bombardment (FAB) mass spectrometry (MS), cross-chiral relationships were confirmed for the first time for the diasteromeric host-guest complexations between the chiral crown ether host (1) and the chiral organic ammonium ion guest (2) on the basis of the relative peak intensities (RPI). Both host-guest combinations (R, R, R, R) - 1, (R) - 2 and (S, S, S, S) - 1, (S) - 2 obviously provided larger RPI values than the combination of both (R, R, R, R) - 1, (S) - 2 and (S, S, S, S) - 1, (R) - 2 by a factor of 1.6 as an averaged value: 1.87 (n = 4)/1.16 (n = 4) = 1.6. These results are consistent with the expected stabilities of the host-guest complexations by CPK model examinations. Successfully observed cross-chiral examinations strongly suggest a potentially useful FABMS/RPI methodology for rapidly searching newly designed and synthesized crown ether-like host compounds with a higher degree of enantioselectivity.