Structural and physicochemical studies of two key intermediates and the impurity in the new synthesis route of vitamin MK-7

Abstract The MK-7 homologues of vitamin K2 are characterized by the best bioavailability among other K vitamins and act effectively in the treatment of osteoporosis and cardiovascular diseases. In this article comprehensive structural studies of two intermediates 1,4-diethoxy-2-methylnaphtalene (M2) and 1,4-diethoxy-2-methyl-3-[(2E)-3-methyl-4-(phenylsulfonyl)-2-buten-1-yl]naphtalene (M3) from the multi-step synthesis of MK-7 vitamin were described. The compounds crystallize in a monoclinic system in P2 1 /n and P2 1 /c for M2 and M3, respectively. Also, the isomer (2 E )-4-chloro-3-methyl-1-(phenylsulfonyl)but-2-ene (M1- E verso) was isolated and the single crystal studies were performed. These three compounds were fully characterized by the 1D and 2D NMR technique as well as by Fourier-transformed infrared and Raman spectroscopies.