title: Scalar Cross-Relaxation Detected in the NOESY Spectra of Oxazolidines and Thiazolidines.
abstract: Anomalous cross-peaks observed in the NOESY spectra of 2,4-disubstituted thiazolidines and oxazolidines that cannot be attributed to classical dipolar NOE or chemical exchange peaks have been investigated experimentally and computationally and have been shown to arise from scalar cross-relaxation of the first kind. This process is stimulated by the relatively slow modulation of scalar couplings and, for the systems studied, arises from slow on-off proton exchange of the amino nitrogen, a process influenced by solution temperature, acidity, and concentration. The mechanism is likely to be significant for many systems in which proton exchange occurs on the millisecond time scale, and misinterpretation of these cross-peaks may lead to erroneous conclusions should their true origins not be recognized.
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K.
authors.forename: Tharindi D
authors.initials: TD
authors.lastname: Panduwawala
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K.
authors.forename: Laia
authors.initials: L
authors.lastname: Josa-Culleré
authors.affiliation: School of Chemistry, University of Southampton , Highfield Campus, Southampton SO17 1BJ, U.K.
authors.forename: Ilya
authors.initials: I
authors.lastname: Kuprov
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K.
authors.forename: Barbara
authors.initials: B
authors.lastname: Odell
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Moloney
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K.
authors.forename: Timothy D W
authors.initials: TD
authors.lastname: Claridge