title: Diastereoselective fragmentation of chiral alpha-aminophosphonic acids/metal ion aggregates.
abstract: Diastereomeric clusters of general formula [MAB(2)](+) and [MA(2)B](+) (M = Li(I), Na(I), Ag(I), Ni(II)-H, or Cu(II)-H; A = (R)-(-)- and (S)-(+)-(1-aminopropyl)phosphonic acid; B = (1R)-(-)- and (1S)-(+)-(1-aminohexyl)phosphonic acid) have been readily generated in the electrospray ionization (ESI) source of a triple-quadrupole mass spectrometer and their collision-induced dissociation (CID) investigated. CID of diastereomeric complexes, e.g. [MA(S)(B(S))(2)](+) and [MA(R)(B(S))(2)](+), leads to fragmentation patterns characterized by R(homo) = [MA(S)B(S)](+)/[M(B(S))(2)](+) and R(hetero) = [MA(R)B(S)](+)/[M(B(S))(2)](+) abundance ratios, which depend upon the relative stability of the diastereomeric [MA(S)B(S)](+) and [MA(R)B(S)](+) complexes in the gas phase. The chiral resolution factor R(chiral) = R(homo)/R(hetero) is found to depend not only on the nature of the M ion but also on that of the fragmenting species, whether [MAB(2)](+) or [MA(2)B](+). The origin of this behavior is discussed.
authors.affiliation: Dipartimento di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università di Roma La Sapienza, I-00185 Roma, Italy.
authors.forename: Antonello
authors.initials: A
authors.lastname: Filippi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Speranza
authors.forename: Alessandra
authors.initials: A
authors.lastname: Paladini
authors.forename: Roberta
authors.initials: R
authors.lastname: De Carolis
authors.forename: Anna Giardini
authors.initials: AG
authors.lastname: Guidoni
authors.forename: Aldo
authors.initials: A
authors.lastname: Laganà
authors.forename: Mauro
authors.initials: M
authors.lastname: Satta