CHIRALITY-DIRECTED SELF-ASSEMBLY OF SUPRAMOLECULAR PROPELLERS OF DIALKYLTARTRATE TRIMERS WITH HYDRONIUM, AMMONIUM AND PRIMARY AMINIUM IONS IN CI MASS-SPECTRA

The specific non-covalent gas phase association of chiral dialkyltartr ates M with multiprotic onium ions A . H+, such as hydronium, ammonium and primary aminium ions, was investigated by chemical ionization (CI ) mass spectrometry. The method applies enantiomer-labeled racemates o f dimethyl-(S)- and [H-2(6)]dimethyl-(R)-tartrate (s and r) and diisop ropyl-(S)- and [H-2(14)]diisopropylyl-(R)-tartrate (S and R). Unusuall y stable trimer adduct clusters M-3.AH(+) were observed (5%-50% of the substrate ions). The abundances of the four diastereomers rrr.AH(+), rrs.AH(+), rss.AH(+) and sss.AH(+) did not show the statistics 1:3:3:1 , but a pattern ranging from 1:1:1:1 to 5:3:3:5. Thus the homochiral c lusters rrr.AH(+) and sss.AH(+) are three to five times more favored t han the heterochiral ions. for the primary amines 1-10 as base A the c hiral effect mainly depends on the CI conditions and hardly on the ami ne properties (proton affinity, steric crowding, chirality). For ammon ia and water as based A the chiral effect was 2.1 and 2.7-3.6 respecti vely. The effect was not found in M-3.AH(+) have an especially stable supramolecular propeller structure as supported by PM3 calculations. T he clusters allow CI experiments for molecular and chiral recognition. (C) 1997 by John Wiley & Son, Ltd. No. of Figures:7 No. of Tables:2 N o. of Refs:32.