Process for the preparation of MK-7 type of vitamin K 2, represented by formula comprising the steps of: (a) reacting an α-sulfonyl carbanion generated in situ from the phenylsulfone of monoprenylmenadiol derivative of formula wherein R 1 represents ethyl, in the presence of a strong organometallic base, with a hexaprenyl halide of formula wherein X represents bromine, one of Z' and Z" is H and the other is a phenylsulfonyl -SO 2 Ph group, as an alkylating agent; to yield the phenylsulfonyl derivative of menadiol of the formula (VIII) wherein R 1, Z' and Z" have the meaning defined above, (b) removing the phenylsulfonyl groups from the menadiol derivative of formula (VIII) by the reductive elimination, to yield the menadiol derivative of formula wherein R 1 has the meaning defined above; (c) subjecting the menadiol derivative of formula to an oxidative deeterification, to yield the crude menadione compound of formula, (d) optionally, purifying the crude menadione compound of formula to yield pure MK-7; wherein the hexaprenyl halide of formula is obtained in the process comprising the steps of: (i) alkylating the two triprenyl units of formulae and wherein: if one of the Y' and Y" represents the phenylsulfonyl -SO 2 Ph group, then the other Y' or Y" represents the halogen atom, in the presence of a strong base, to yield the compound of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, (ii) removing the acetyl group from the compound of formula, to yield the hexaprenol derivative of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, (iii) reacting the compound of formula with a halogenating agent, to yield the phenylosulfonyl-hexaprenyl halide of formula wherein X represents bromine, and Z' and Z" have the meaning defined above for the formula. (a) reacting an α-sulfonyl carbanion generated in situ from the phenylsulfone of monoprenylmenadiol derivative of formula wherein R 1 represents ethyl, in the presence of a strong organometallic base, with a hexaprenyl halide of formula wherein X represents bromine, one of Z' and Z" is H and the other is a phenylsulfonyl -SO 2 Ph group, as an alkylating agent; to yield the phenylsulfonyl derivative of menadiol of the formula (VIII) wherein R 1, Z' and Z" have the meaning defined above, (b) removing the phenylsulfonyl groups from the menadiol derivative of formula (VIII) by the reductive elimination, to yield the menadiol derivative of formula wherein R 1 has the meaning defined above; (c) subjecting the menadiol derivative of formula to an oxidative deeterification, to yield the crude menadione compound of formula, (d) optionally, purifying the crude menadione compound of formula to yield pure MK-7; wherein the hexaprenyl halide of formula is obtained in the process comprising the steps of: (i) alkylating the two triprenyl units of formulae and wherein: if one of the Y' and Y" represents the phenylsulfonyl -SO 2 Ph group, then the other Y' or Y" represents the halogen atom, in the presence of a strong base, to yield the compound of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, (ii) removing the acetyl group from the compound of formula, to yield the hexaprenol derivative of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, (iii) reacting the compound of formula with a halogenating agent, to yield the phenylosulfonyl-hexaprenyl halide of formula wherein X represents bromine, and Z' and Z" have the meaning defined above for the formula. (i) alkylating the two triprenyl units of formulae and wherein: if one of the Y' and Y" represents the phenylsulfonyl -SO 2 Ph group, then the other Y' or Y" represents the halogen atom, in the presence of a strong base, to yield the compound of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, if one of the Y' and Y" represents the phenylsulfonyl -SO 2 Ph group, then the other Y' or Y" represents the halogen atom, in the presence of a strong base, to yield the compound of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, (ii) removing the acetyl group from the compound of formula, to yield the hexaprenol derivative of formula wherein one of Z' and Z" represents H and the other represents the phenylsulfonyl -SO 2 Ph group, (iii) reacting the compound of formula with a halogenating agent, to yield the phenylosulfonyl-hexaprenyl halide of formula wherein X represents bromine, and Z' and Z" have the meaning defined above for the formula. X represents bromine, and Z' and Z" have the meaning defined above for the formula.