Download full text in PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... The title reaction yields (3R,5R) and (3R,5S) isomers of methyl 5-cyanotetrahydro-1,4-2H-thiazine -3-carboxylate, together with methyl 2-acetylthiazole-4-carboxylate as a minor by-product. The stereochemistry of the tetrahydrothiazine derivatives is discussed.