title: Diastereoselective protocols for the synthesis of 2,3-trans- and 2,3-cis-6-methoxy-morpholine-2-carboxylic acid derivatives.
abstract: Two diastereoselective and straightforward protocols for the high-yielding synthesis of 2,3-trans- and 2,3-cis-6-methoxy-3-substituted morpholine-2-carboxylic esters were realized in few steps, through the condensation between 5,6-diethoxy-5,6-dimethyl-1,4-dioxan-2-one and an appropriate imine, which is the key reaction to control the C2-C3 relative stereochemistry, followed by a methanolysis/ring-closure tandem reaction sequence. In particular, 2,3-trans-morpholines derive from the R*,S*-product of the acid condensation of N-functionalized alkylimines with the silylketene acetal of the above lactone, whereas 2,3-cis-morpholines derive from the R*,R*-product of basic condensation of an N-tosylimines with the lactone.
authors.affiliation: CNR--Institute of Molecular Science and Technology (ISTM), Milano, Italy. michele.penso@istm.cnr.it
authors.forename: Michele
authors.initials: M
authors.lastname: Penso
authors.forename: Francesca
authors.initials: F
authors.lastname: Foschi
authors.forename: Sara
authors.initials: S
authors.lastname: Pellegrino
authors.forename: Andrea
authors.initials: A
authors.lastname: Testa
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Gelmi