The chemical reactions and pathways resulting in the formation of any of the menaquinones. Structurally, menaquinones consist of a methylated naphthoquinone ring structure and side chains composed of a variable number of unsaturated isoprenoid residues. Menaquinones that have vitamin K activity and are known as vitamin K2.
Source:
GOC:jl,
http://www.dentistry.leeds.ac.uk/biochem/thcme/vitamins.html#k