The Collaborative International Dictionary of English v.0.48:

vitamin K1 \vitamin K1\ n.
   one of the two K vitamins, (C31H46O2). It is fat-soluble
   and occurs naturally as the trans isomer. Chemically it is
   2-methyl-3-phytyl-1,4,-naphthoquinone.

   Syn: phylloquinone, phytonadione, antihemorrhagic vitamin..
        [WordNet 1.5 +PJC] vitamin K2