Abstract
Vitamin-K is a demanding multi-functional health product in the market and belongs to a class of isoprenoid molecules that comprises methylnaphthoquinone (MK) unit attached to an isoprene side chain. They are fat soluble and differ in the extent of side chain & obtained in the nature as vitamin K1 (phylloquinone), menaquinone/vitamin K2, and other lipoquinones. Owing to their owned polyprenyl side chain, they are hydrophobic/lipophilic in nature. Generally, the synthesis of vitamin K and its variants suffers with isomerization (for example 11 isomers were identified for cis/trans MK-7). Naturally, in bio-systems vitamin K produces through shikimic acid pathway and terpene biosynthetic pathway for the synthesis of menaquinone part & prenyl side chain parts respectively. Menadione or its auxiliaries are commonly being used as substrates to the synthesis of vitamin K variants through the involvement of condensation reactions, Friedel-Craft alkylation’s, Claisen rearrangement, Diels-Alder reactions and others. Importantly, organometallic reagents, such as Grignard, Gilman, organotelluride and other reagents could be the promising and consistent choice of substrate to the synthesis of various vitamin K’s. Vitamin K is well known for blood coagulation. As an antihaemorrhagic vitamin, it’s also being the current interest for the treatment of bone and vascular diseases. In addition, vitamin k is indispensable for the activation of vitamin K dependent (VKD) proteins and that are present almost in all tissues and responsible for hemostasis, bone mineralization, arterial calcification, apoptosis, phagocytosis, growth control, chemotaxis, and signal transduction. This chapter summarizes various synthetic approaches of vitamin K & derivatives and their biological functions.
Highlights
Vitamin K is a family of natural products, comprises vitamin K1, vitamin K2 and vitamin K3
Vitamin K2 are varied on the basis of number of isoprene units present in the side chain and they denoted as MK-n (n – number of isoprene units; Figure 1)
The Vitamin K2 presents naturally in eggs, meet, fermented foods present in bacteria, for example, MK-9 is found in mycobacterium with nine isoprene units and its reduced derivative at second isoprene unit MK-9(II-H2) could be active as electron transport agent in [3, 7]
Summary
Vitamin K is a family of natural products, comprises vitamin K1 (phylloquinone), vitamin K2 (methylnaphthoquinones/menaquinones-MK) and vitamin K3 (menadione) These are structurally methylated napthoquinones possess isoprene side chain (vitamin K1 & vitamin K2) and they vary in the extent of isoprene side chain, in terms of number of isoprene units and its level of saturation [1–5]. The Vitamin K2 presents naturally in eggs, meet, fermented foods (natto, cheese, yogurt and sauerkraut) present in bacteria, for example, MK-9 is found in mycobacterium with nine isoprene units and its reduced derivative at second isoprene unit MK-9(II-H2) could be active as electron transport agent in [3, 7] In humans, these menaquinones display several biological properties, including facilitating blood coagulation [8, 9]. Its required to supply an adequate amount through the dietary sources
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