The invention relates to the process for the preparation of sulphonyl derivatives of cholecalciferol and to the novel intermediate compounds isolated in this method. Especially, the invention relates to the process for the preparation of cholecalciferol derivatives with C-22 sulphonyl substituent, useful in the synthesis of vitamin D analogues modified in the aliphatic side chain. In particular, C-22 sulphonyl derivatives of cholecalciferol may be used in the synthesis of pharmacologically active vitamin D analogs with multiple bonding, preferably double bond, at C-22, such as calcipotriol . According to the description of the International Patent Publication WO 03/087048, the preparation method of cholecalciferol derivatives with a C-22 sulphonyl substituent of Formula 1 on the enclosed Scheme I, wherein Ri is a protective group, where R2 is a heterocyclic group, such as 2-thiazolyl, 2- benzothiazolyl, l-phenyl-lH-tetraz-5-yl, 2-pyridyl, 2- pyrimidynyl, 1-isochinolinyl, l-methyl-2-imidazyl, 4- alkyl-l,2,4-triaz-3-yl, comprises immediate oxidation of the proper vitamin D sulfide of Formula 3, obtained from the hydroxy1 derivative of Formula 2. Due to the presence of a triene system sensitive to oxidizing agents, there is a necessity to carry out the oxidation at moderate temperature. In such conditions significant amounts of intermediate S-oxides are formed, apart from the main product - the sulphonyl compound. In the described process the possibility of raising the temperature of the reaction to completely transform intermediate sulfides to a corresponding sulphonyl compound is very limited, due to a competitive oxidation reaction of the triene system. A complete separation of the final sulphonyl derivative from the intermediate sulfides is associated with significant preparation difficulty, particularly at scale-up, and decrease of yield of the reaction. Thus, the protection of the triene system was considered appropriate, which would not only allow for effective oxidation of sulfide to sulphone, but also did not result in excessive prolongation of the synthetic procedure related to an additional step of deprotection, and moreover allow for a reconstruction of a desired double bond system in the oxidation product. Protection methods of the triene system are known in the art and often applied in vitamin D chemistry. Thus, as a result of solvolysis of vitamin D tosylate in aqueous acetone, obtained was (6JR) -hydroxy- 3, 5-cyclo-vitamin D system, comprising only isolated double bonds (Mazur and Sheves, J. Am. Chem. Soc. 97, 6249, 1975) . This system was proved particularly convenient for functionalization of vitamin ring A at the biologically significant C-I. Reconstruction of the triene system was carried out in acidic conditions, leading to a mixture of {5E,1E) and {5Z,1E) isomers. Barton et al. (J. Chem. Soc. Perkin Trans 1, 829, 1976) obtained an isomeric mixture of tricarbonyl iron complexes, coordinating bonds 5,6 and 10,19 of the triene system. The reconstruction of the triene system was carried out in the mild conditions under ferric chloride. However, none of these systems were proper for the oxidating and regioselective double bond cleavage in the side chain. Not until Aberhart (J. Org. Chem.., 41, 2098, 1976) and, independently, Reischl {Monatsh. Chem., 113, 439, 1982) have observed that the vitamin D triene system forms Diels-Alder adducts with dienophiles, such as 4-phenyl-l, 2, 4-triazoline-3, 5-dione or phthaloyl-1, 4- dione. In a reaction of a mixture of isomeric C-6 adducts with ozone, a regioselective double bond cleavage in the side chain is observed. However, deprotection of {5E,1E) vitamin in alkaline conditions (e.g. potassium hydroxide in boiling methanol, buthanol or ethylene glycol) runs with limited yield and only after many hours (M. Chodyήski et al., Steroids, 67, 789, 2002) . Particularly convenient was the protection of triene system in the adduct form with sulfur dioxide developed independently by Yamada (Chem. Lett., 583, 1979) and Reischl {Helv. Chim. Acta, 62, 1763, 1979) . These adducts are obtained in a quantitative yield, by passing sulfur dioxide through a benzene-water solution vitamin D, as a mixture of epimers at the C-6. Thermolysis of adduct mixture in boiling ethanol results in reconstruction of triene system isomer (5E,1E) . It has been recently observed that using of C-22 sulfide derivatives of cholecalciferol protected as Diels-Alder adducts in the oxidation, although this involves the necessity of inversion of configuration of thus obtained sulphone, it provides for technological advantages, which compensate for the extension of the synthesis by an additional photoisomerization step. These advantages include elimination of forming of S-oxides by-product, which results from possibility of applying higher temperature in the. oxidation of sulfide to sulphone and high yield of the process resulting from almost complete conversion of the substrate. Moreover, the method provided in the invention gives a difficult to predict, in the light of prior art literature, facility of sensitized photoisomerization of the compound comprising both {5E,1E) triene system and C-22 sulphonyl. In the process of photoisomerization, regrouping or decomposition of this arrangement was not observed and the process is carried out with high yield, exceeding 80%. The process according to the invention of preparation of sulphonyl derivatives of cholecalciferol of formula 1, wherein Ri is protective group, preferably t-butyl (dimethyl) silyl, where R2 is heterocyclic group, such as 2-thiazolyl, 2-benzothiazolyl, 1-phenyl-lH- tetrazo-5-yl, 2-pyridyl, 2-pyrimidynyl, 1-isochinolinyl, l-methyl-2-imidazyl, 4-alkyl-l, 2, 4-triazo-3-yl, consists in the use of hydroxyl derivative of cholecalciferol as a starting material, in which the triene system is protected as an Diels-Alder adduct, this adduct is subjected to reaction with thiol of formula HS-R2, wherein R2 is as in Formula 1, then sulfide adduct is oxidized to sulphone adduct, protection is removed by thermolysis and the resulting (5E,7E) sulphone of Formula 5 is subjected to sensitized photoisomerization to give (5Z,7E) sulphone of Formula 1. In case of the subject invention, the protection of the starting hydroxyl derivative of cholecalciferol as adduct with sulfur dioxide proved to be particularly favorable. The adduct is not only easily obtained, but is as easily deprotected after the reaction. The method for the realization of the invention exemplified by adduct with sulfur dioxide of Formula 2a is presented in Figure 2. Sulfide adducts of Formula 3a and sulphon adducts of Formula 4 isolated in the method provided in the invention, wherein Ri is protective group, where R2 is heterocyclic group, such as 2-thiazolyl, 2- benzothiazolyl, l-phenyl-lH-tetrazo-5-yl, 2-pyridyl, 2- pyrimidynyl, 1-isochinolinyl, l-methyl-2-imidazyl, 4- alkyl-1,2, 4-triazo-3-yl, are novel cholecalciferol derivatives, not described in the literature. Particularly favorable are novel derivatives according to the invention of Formula 3a and 4, wherein Ri is t-buthyl (dimethyl) silyl, where R2 is 2- benzothiazolyl. According to the invention, adduct of the hydroxyl derivative of cholecalciferol of Formula 2a is converted directly into an adduct of the sulfide of Formula 3a under Mitsunobu reaction conditions with thiol of formula HS-R2, wherein R2 is heterocyclic group, preferably with 2-mercaptobenzothiazole and triphenylophosphine, in the presence of diisopropyl aza-dicarboxylate in the solution of methylene chloride at lower temperature. Oxidation to sulphon of formula 4 is carried out with ammonijαm molybdate tetrahydrate - hydrogen peroxide system in ethanol under elevated temperature. Adduct protection is removed by thermolysis, e.g. with sodium dicarbonate in boiling alcohol, such as methanol, ethanol, butanol or ethylene glycol. The sulphonyl derivatives of cholecalciferol comprising (5E, 7E) triene system of Formula 5 obtained according to the invention demonstrate a unique, in the group of vitamin D compounds, strong tendency to crystallization. This allows for their convenient use in the synthesis of vitamin D analogs to facilitate the removal of impurities from previous steps, without the necessity of usually applied precise purification of intermediate compounds. Photoisomerization of (5E,7E) triene system sulphonyl derivative to (5Z,7E) triene system is carried out according to the method known in the field of vitamin D chemistry, with the yield exceeding 80%. Sulphonyl derivatives of cholecalciferol with (5Z, 7E) -triene system, obtained according to the method according to the invention, are valuable starting material in the synthesis of various vitamin D derivatives. The invention is further illustrated by the following non-limiting examples.

Example 1 Preparation of (6RS) -SO2- [5E, IE) - (IS, 3JR) -1, 3-bis [t- butyl (dimethylsilyl) oxy] -22-thiobenzothiazolyl-23, 24- dinor-9, lO-secochola-5 (10) , 7-diene adduct [R2 = thiobenzothiazolyl, Ri = t-butyl (dimethyl) silyl] . In a 1 L round bottom flask with crude (6.RS)-SO2- (5E,1E) - (IS, 3.R)-I, 3-bis [t-butyl (dimethyl-silyl) oxy] -22- hydroxy-23,24-dinor-9,10-secochola-5 (10) ,7-diene adduct (ca.116 g, content of pure compound ca. 90 g) 500 ml of CH2CI2 was added and the obtained solution was transferred to a dropping funnel. In another round bottom flask (2 L) a suspension of 45 g of 2-thiobenzothiazole in 500 ml of CH2Cl2 was prepared. The flask was placed in a cooling bath (00C) on a magnetic stirrer. Then 71 g of triphenylphosphine was added in single portion with stirring and the above prepared solution of alcohol of Formula 1 in CH2Cl2 was slowly added dropwise. Then 45 mL of diisopropyl azadicarboxylate was added dropwise. The mixture was vigorously stirred for 90 min. at 00C. The cooling bath was removed; 4 L of brine and 200 mL of water was added. The organic phase was separated, and the residue was extracted with CH2Cl2 (2 x 200 mL) . The combined organic phases were dried over anhydrous Na2SO4 (80 g) . The solution was filtered and concentrated under reduced pressure. The residue was dissolved in toluene- hexane 1:1 (v/v) mixture and injected on the chromatography column with silica gel (230-400 m, 800 g) . As eluents the following solvents and their mixtures were used: hexane 300 ml, hexane-ethyl acetate 2% 1500 mL, hexane-ethyl acetate 4% 1500 mL, hexane-ethyl acetate 6% 1500 mL, hexane-ethyl acetate 8% 1500 mL. The chromatography course was controlled on TLC in the solvent system hexane-ethyl acetate 12%. The clean fractions were combined and the solvents were evaporated under reduced pressure. The residue (ca. 284 g) was dissolved in 600 mL of hexane - toluene 2:1 mixture. The suspension was filtered under reduced pressure using a Buchner funnel. The precipitate on the filter was washed with 1 portion (200 mL) of hexane - toluene 2:1 mixture. The filtrate was concentrated under reduced pressure and thoroughly dried on a vacuum oil pump. Obtained was ca. 160 g of. crude product; 1H-NMR (δ, ppm) 0.06 (12H, m, 2 Si(CH3J2)/ 0.69 (3H, s, 18-CH3), 0.88 (18H, m, 2 Si- C(CH3)3), 1.14 (3H, d, J=β.5 Hz, 21-CH3), 2.62 and 3.01 (3H, m, 6-H and 22-CH2), 3.94 (IH, m, 7-H) , 4.19 and 4.37 (2H, m, 1-H and 3-H) , 4.69 (2H, m, 10'-CH2), 7.34 and 7.77 (4H, m, Ar-H) .

Example 2. Preparation of (6RS) -SO2- (5£, IE) - (IS, 31?) -1, 3-bis [t- butyl (dimethylsilyl) oxy] -22-sulphonylbenzothiazolyl- 23, 24-dinor-9, lO-secochola-5 (10) , 7-diene adduct [R2=sulphonylbenzothiazolyl, Rx=t-butyl (dimethylsilyl) ] . Three neck flask (4 L) fitted with mechanical stirrer and dropping funnel was placed in a water bath and ca. 160 g of crude (6RS) -SO2- {5E, IE) - (IS, 3R) -1, 3-bis [t- butyl (dimethylosilyl) oxy] -22-thiobenzothiazolyl-23,24- dinor-9, 10-secochola-5 (10) , 7-diene adduct in 400 mL of CH2Cl2 and 1200 mL of C2H5OH were added. The stirrer was started and solution of 35 g of ammonium heptamolibdenate hydrate (AHT) in 230 mL of H2O2 (35%) was dropped in over ca. 5 minutes. The temperature of the water bath was elevated to 65°C and the stirring was continued for ca. 2.5 hours until complete disappearance of the substrate (controlled by TLC) . The mixture was cooled to 00C and 1400 πiL of 10% solution of Na2SC>3 was dropped in until the disappearance of peroxides (indicator paper) . The solvents were removed under reduced pressure, and IL of ethyl acetate was added to the residue. The organic phase was separated and the water phase was extracted twice with ethyl acetate (2 x 500 mL) . The combined organic phases were dried over anhydrous Na2SO4 (50 g) and filtered to a 3 L flask. The solvents were removed under reduced pressure, and the residue was dried on a vacuum oil pump. Obtained was ca. 145 g of crude mixture of sulphones as a yellow foam oil; IR, v, 2952, 2928, 2883, 2856, 1624, 1472, 1381, 1360, 1323, 1253, 1148, 1121, 1083, 834, 760 cm"1; 1H-NMR (δ, ppm) 0.06 (12H, m, 2 Si(CHa)2), 0.65 (3H, s, 18-CH3), 0.87 (18H, m, 2 Si- C(CH3J3), 1.28 (3H, d, J=6.5 Hz, 21-CH3), 3.28 and 3.65 (3H, m, 6-H and 22-CH2), 3.94 (IH, m, 7-H) , 4.17 and 4.36 (2H, m, 1-H and 3-H)1. 4.65 (2H, m, 10'-CH2), 7.61, 8.02 and 8.22 (4H, m, Ar-H) .

Example 3. Preparation of (5E, IE) - (IS, 3R) -1, 3-bis [t-butyl (dimethylosilyl) oxy] -22-sulphonylbenzothiazolyl-23,24- dinor-9, lO-secochola-5, 7, 10 (19) -triene [R3=sulphonylbenzothiazolyl, Ri=t-butyl (dimethyl) silyl] . To a round bottom 3 L flask with (6RS) -SO2- (5E,1E) - (IS, 3R) -1, 3-bis [t-butyl (dimethylsilyl) oxy] -22- sulphonylbenzothiazolyl-23, 24-dinor-9, 10-secochola- 5 (10) ,7-diene adduct 1700 mL of ethanol was added. The flask was fitted with a reflux condenser and placed in a heating bowl and placed over a magnetic stirrer. Then 100 g of NaHCO3 was added and continuously stirred heated under reflux over 3 hours (TLC, hexane-ethyl acetate 16%) . The mixture was cooled, the stirrer removed and solvents were removed under reduced pressure. Then 800 mL of water and 800 mL of ethyl acetate was added. The organic phase was separated and the residue was extracted with two portions of ethyl acetate (2 x 250 mL) . The combined organic phases were dried over anhydrous Na2SO4 (100 g) and filtered to bottom round flask (3 L) . The solvents were removed under reduced pressure. The residue was dissolved in toluene and injected on the chromatography column with aluminium oxide (1:10) in hexane. Hexane was used to wash out toluene from the column. Product was washed with a 10% mixture of hexane - ethyl acetate. Solvents were removed under reduced pressure to give ca. 5O g of light yellow oily mixture of products. Then ca. 35 mL of ethyl acetate was added, and the mixture was heated near boiling point and 900 mL of methanol was added in one portion. The mixture was left at -2O0C for 24 hours. The precipitate was filtered and washed with one portion of cold methanol (100 mL) . The precipitate was dried to the constant weight on a vacuum oil pump. Obtained was ca. 24 g of product used in the next reaction without further purification. UV λmax (EtOH) 271.0, 240.6, 207.0 nm, Kin 245.6, 231.0 nm; IR, v, 2951, 2928, 2883, 2856, 1636, 1554, 1472, 1324, 1252, 1147, 1083, 834, 760 cm"1; 1H-NMR (δ, ppm) 0.06 (12H, m, 2 Si (CH3) 2) f 0.56 (3H, s, 18-CH3), 0.85 (18H, m, 2 Si- C (CH3) 3), 1.26 (3H, d, J=β,7 Hz, 21-CH3), 3.31 and 3.62 (2H, m, 22-CH2), 4.22 (IH, m, 3-H) , 4.53 (IH, m, 1-H) , 4.97 (2H, m, 19E-H and 19Z-H) , 5.79 (IH, d, J=Il.5 Hz, 7- H), 6.42 (IH, d, J=Il.5 Hz, 6-H) , 7.62, 8.04, 8.23 (4H, m, Ar-H) .

Example 4. Preparation of (5Z, IE) - (IS, 3R) -1, 3-bis [t- butyl (dimethylsilyl) oxy] -22-sulphonylbenzotiazolyl-23, 24- dinor-9, lO-secochola-5, 7, 10 (19) -triene [R2=sulphonylbenzothiazolyl, Ri=t-butyl (dimethyl) silyl] . (5E, IE) - (IS, 3R) -1, 3-Bis [t-butyl (dimethylsilyl) oxy] - -22-sulphonylbenzothiazolyl-23, 24-dinor-9, 10-secochola- 5, 7, 10 (19) -triene (24 g) was dissolved in a mixture toluene - methanol 5:1 (3 L), saturated with argon. Then 24 g of anthracene was added. The solution was placed in a UV irradiation apparatus and the operation of circulating pump and power supply for UV lamps were turned on. Exposure was carried out for 3.5 hours at 18°C-20°C, until the disappearance of substrate (TLC, hexane-ethyl acetate 40:1) . The solvents were removed under reduced pressure. Then 400 πiL of hexane was added to the residue and left for 6 hours at -200C. The mixture was filtered in vacuo through a Shott funnel, the precipitate was washed with cold hexane (50 mL) . The residue was dissolved in 450 mL of toluene and the filtered solution of 2.4 g of maleic anhydride in 50 mL of toluene. The mixture was saturated with argon and stirred for 12 hours on a magnetic stirrer at room temperature. Solvents were removed under reduced pressure. The residue was dissolved in a mixture of 15 mL of toluene and 15 mL of hexane and injected on the chromatography column filled with 350 g of gel 230-400 mesh. As eluents the mixtures of hexane-ethyl acetate were used: hexane 1000 ml, hexane-ethyl acetate 1% 1500 ml, hexane-ethyl acetate 2% 1000 ml, hexane-ethyl acetate 4% 2500 mL. From the combined fractions containing the product (TLC, hexane-acetate 18%) solvents were removed under reduced pressure. Obtained was ca. 21 g of product as a yellow precipitate. The precipitate was dissolved in 30 mL of ethyl acetate at temperature near boiling point and 700 mL of methanol was added in one portion. The solution was left at - 200C for 24 hours. The precipitate was separated using a Buchner funnel, washed with cold methanol (100 mL) and dried to the constant weight on a vacuum oil pump. Obtained was 17.5 g of (52, IE) - (IS, 3R) - 1, 3-bis [t-butyl (dimethylsilyl) oxy] -22- sulphonylbenzothiazolyl-23,24-dinor-9, 10-secochola- 5,7, 10 (19) -triene as a colorless fluffy powder; UV λmaχ (EtOH) 268.2, 240.0, 214.4 nm, A^in 245.6, 231.0 nm; IR, v, 2951, 2928, 2883, 2856, 1636, 1554, 1472, 1324, 1252, 1147, 1083, 834, 760 cm"1; 1H-NMR (δ, ppm) 0.06 (12H, m, 2 Si(CH3J2, 0.55 (3H, s, 18-CH3), 0.87 (18H, m, 2 Si- C(CH3J3), 1-26 (3H, d, J=6.6 Hz, 21-CH3), 3.28 and 3.65 (2H, m, 22-CH2), 4.18 (IH, m, 3-H) , 4.36 (IH, m, 1-H) , 4.83 (IH, m, 19Z-H) , 5.16 (IH, m, 19E-H) , 5.99 (IH, d, J=Il.4 Hz, 7-H) , 6.21 (IH, d, J=Il.4 Hz, 6-H)1 7.61, 8.02, 8.22 (4H, m, Ar-H) .