title: Diastereoselectivity in Organometallic Additions to the Carbonyl Group of Protected Erythrulose Derivatives.
abstract: We have investigated a number of nucleophillic additions to L-erythrulose derivatives (4-12) bearing protective O-silyl, O-benzyl, and O-trityl groups in various relative positions. The results are discussed in the frame of chelated vs nonchelated transition states with additional support of previously published theoretical calculations. Sound evidence appears to exist for the formation of alpha-chelates as the key intermediates in nucleophillic additions to these alpha,beta-dioxygenated ketones. Since such evidence is still lacking in the case of beta-chelates, proposals of their intermediacy have been relegated in favor of the more solid Felkin-Anh model, which predicts the same stereochemical result. The behavior of these highly functionalized ketones does not always match that of structurally similar aldehydes.
authors.affiliation: Departamento de Química Orgánica, Universidad de Valencia, E-46100 Burjassot, Valencia, Spain, and Departamento de Química Inorgánica y Orgánica, Universidad Jaume I, E-12080 Castellón, Spain.
authors.forename: J. Alberto
authors.initials: JA
authors.lastname: Marco
authors.forename: Miguel
authors.initials: M
authors.lastname: Carda
authors.forename: Florenci
authors.initials: F
authors.lastname: González
authors.forename: Santiago
authors.initials: S
authors.lastname: Rodríguez
authors.forename: Encarna
authors.initials: E
authors.lastname: Castillo
authors.forename: Juan
authors.initials: J
authors.lastname: Murga