Catalysis of the reaction: 3-hydroxy-2-methyl-3-phytyl-2,3-dihydronaphthoquinone + oxidized dithiothreitol + H2O = 2,3-epoxy-2,3-dihydro-2-methyl-3-phytyl-1,4-naphthoquinone + 1,4-dithiothreitol.
vitamin K 2,3-epoxide reductase activity