Stereocontrolled Syntheses of Epimeric 3-Aryl-6-phenyl-1-oxa-7-azaspiro[4.5]decane NK-1 Receptor Antagonist Precursors

[structure: see text]. Complementary stereoselective syntheses of individual C3 epimers of the NK-1 receptor antagonist precursor 1 have been developed. Both diastereomers were derived from the common intermediate 3; introduction of the 3S stereocenter in 1a was achieved through hydrogenation of an arylated dihydrofuran, whereas the corresponding stereogenic center in 1b was installed using a stereo- and regioselective alkene hydroarylation.