PL190804B1 - Method of obtaining active vitamin d metabolites and new intermediate compounds - Google Patents

Abstract

. The method of obtaining active metabolites of vitamins D of general formula I, in which X is a hydrogen atom or a hydroxyl group, characterized in that the deprotonated sulfone an alkyl isohexyl ether of the formula 2, where R3 is a protecting group, such as an alkylsilyl or alkoxyalkyl group containing from 1 to 6 carbon atoms, alkylates with the appropriate vitamin tosylate Formula 3 wherein X is H or OR1 and R1 is a protecting group a hydroxyl function such as an alkylsilyl group or alkoxyalkyl containing from 1 to 6 carbon atoms, wherein R1 and R3 are the same or different in the presence of a strong organic base in an aprotic solvent, then the resulting mixture of vitamin sulfones Formula 4 wherein the substituents have the above defined meaning is reacted desulfonylation with an alkali metal amalgam, preferably sodium amalgam in buffered methanol then discarded protecting groups.

Description

The subject of the invention is a new method for the preparation of active vitamin D metabolites as well as new intermediates used in this method.

Active metabolites of vitamin D have a regulating effect on calcium-phosphate homeostasis in the body and are used as medicaments in the treatment of a variety of metabolic and skeletal disorders, including osteoporosis. Moreover, 1,25-dihydroxycholecalciferol (calcitriol) has an antiproliferative effect and favorably stimulates differentiation of a number of tumor cell lines and epidermal keratinocytes. For this reason, it can be used in the treatment of cancer and skin diseases such as psoriasis.

The method of obtaining active metabolites of cholecalciferol from a steroid precursor, known from the United States patent no. - and thermoisomerization and the Grignard reaction. The intermediate 23α-vitamin homoester is converted to the corresponding 1α-hydroxy derivative and 1,25-dihydroxy-cholecalciferol is obtained in a subsequent Grignard reaction.

Other known methods consist in converting 25-hydroxycholesterol into the corresponding 5,7-diene which, by photo- and thermoisomerization, forms 25-hydroxycholecalciferol (German Patents Nos. 1,933,375 and 2,415,676).

All these methods use steroidal raw materials of natural origin (e.g. 25-hydroxycholesterol), which are available in limited quantities and do not allow the scale-up of the production of active vitamin D metabolites.

The aim of the invention is to develop a practical and efficient method of synthesizing active vitamin D metabolites from available vitamin intermediates, without the need to use toxic and inconvenient reagents.

The present invention is based on a process for the preparation of active vitamin D metabolites of the general formula I, in which X is a hydrogen atom or a hydroxyl group, characterized in that the deprotonated alkyl isohexyl ether sulfone of the formula II in which R3 is a protecting group such as an alkylsilyl or alkoxyalkyl group containing from 1 to 6 carbon atoms are alkylated with the corresponding vitamin tosylate of formula 3, wherein X is H or OR1, and R1 is a group protecting a hydroxyl function, such as an alkylsilyl or alkoxyalkyl group containing from 1 to 6 carbon atoms, with R1 and R3 are the same or different in the presence of a strong organic base in an aprotic solvent, the resulting mixture of vitamin sulfones of formula IV, wherein the substituents are as defined above, is desulfonylated with an alkali metal amalgam, preferably sodium amalgam in buffered methanol, and then removes the protecting groups.

The method according to the invention is illustrated in the diagram in Fig. 3.

A protecting group for a hydroxyl function is any protecting group used in vitamin D chemistry such as an alkylsilyl or alkoxyalkyl group containing from 1 to 6 carbon atoms. After the reaction has ended, the silyl groups are removed in a known manner, for example under acidic conditions, by treatment with solutions of protic acids or their salts with organic bases in organic solvents.

The invention also relates to novel vitamin sulfones represented in Figure 2 by formula 4, wherein X is H or OR1, and R1 and R3 are the same or different and represent a protecting group. The new sulfones, which are a mixture of stereoisomers differing in configuration at the C-23 carbon atom, are intermediates isolated in the process of the invention.

Also novel are the hydroxyl protected cholecalciferol derivatives represented in Figure 2 by formula 5, wherein X is H or OR1 and R1 and R3 have the previously defined meaning. These derivatives also fall within the scope of the present invention.

The starting materials for the synthesis of active vitamin D analogues, vitamin C-22 tosylates, shown in Figure 3 with general formula 3 are key synthons used in vitamin D chemistry. Tosylanes can be obtained from the corresponding C-22 alcohols by known methods, for example by a method analogous to that described above. in Polish patent application No. P-310 454 for C-25 tosylates obtained from C-25 alcohols.

PL 190 804 B1

The process according to the invention makes it possible to obtain, by a few relatively simple synthesis steps, active metabolites of vitamin D substituted at the C-25 position with a hydroxyl group, such as calcifediol of formula 1 (fig. 1) in which X is hydrogen and calcitriol of formula 1 (fig. 1) wherein X is a hydroxyl group.

The following examples illustrate the invention.

Example 1

Preparation of (3R) - (5Z, 7E) -3-t-butyldimethylsilyl-25-trimethylsilyl-23-phenylsulfonyl-9.10-secocholesta- 5,7,10 (19) -trien-3,25-diol (Formula 4 : X = H, R1 = trimethylsilyl, R3 = t-butyldimethylsilyl)

To a solution of 3-methyl-3-trimethylsilyloxybutylsulfone (40.7 mg, 0.135 mmol) in THF (200 mL) was added a solution of n-BuLi (165 mL, 1.23 M) in hexane at room temperature. The resulting yellow solution was stirred for 15 min, then a solution of (3R) - (5Z, 7E) -24-phenylsulfonyl-3-t-butyldimethylsilyl-25-trimethylsilyl-9,10-seco-22,23-dinorchol-5 was added. , 7.10 (19) -trien-3,25-diol (39.1 mg, 0.067 mmol) in THF (200 mL). The solution was stirred for 3 h and then 2 ml of saturated aqueous NH4Cl solution was added. After extraction with methylene chloride (80 ml) and chromatography on silica gel, unreacted tosylate (19.8 mg) was recovered to give (23.9 mg, 49%) a mixture of (3R, 23R) - and (3R, 23S) - (5Z , 7E) -3-t-butyldimethylsilyl-25-trimethylsilyl-23-phenylsulfonyl-9,10-secocholesta-5,7,10 (19) -trien-3,25-diols.

TLC: RF = 0.63 and 0.50 (methylene chloride).

Example 2

Preparation of (3R) - (5Z, 7E) -3-t-butyldimethylsilyl-25-trimethylsilyl-9,10-secocholesta-5,7,10- (19) -trien-3,25-diol (formula 5: X = H, R1 = trimethylsilyl, R3 = t-butyldimethylsilyl)

To a solution of the sulfone mixture obtained in Example 1 (23.9 mg, 0.033 mmol) in 500 ml of THF was added 500 ml of saturated Na2HPO4 in MeOH and 50 mg of solid Na2HPO4, followed by 300 mg of 5% sodium amalgam. The suspension was stirred for 1.5 h until the reaction had ceased to progress. The slurry was decanted from the precipitate, the precipitate was washed with toluene. The combined solutions were evaporated under reduced pressure. Column chromatography on silica gel (hexane: methylene chloride 3: 1) gave (3R) - (5Z, 7E) -3-t-butyldimethylsilyl-25-trimethylsilyl-9,10-secocholesta-5,7, -10 (19 ) -triene-3.25-diol (10.6 mg, 54.9%) as a colorless oil.

TLC: RF = 0.71 (hexane / methylene chloride 1: 1).

Example 3

Preparation of (3R) - (5Z, 7E) -9,10-secocholesta-5,7,10 (19) -trien-3,25-diol (formula 1a)

1 mg of camphorsulfonic acid was added to the protected diol solution obtained in Example 2 in 500 μΐ of a 1: 1 (v / v) chloroform-methanol mixture, and after 2 h another 1 mg of this acid was added and stirring was continued for another 2 h. NaHCO3 and the mixture was diluted with 1mL of diethyl ether. Removal of solvents and silica gel chromatography afforded (3R) - (5Z, 7E) -9.10-secocholesta-5,7,10 (19) -triene-3,25-diol (4.3 mg, 59.6 % yield) in the form of a colorless oil.

UV (EtOH) = A _max = 264.4 nm, A _min = 213 nm;

HPLC: (Eclipse XDB-C8 column, 20% H2O in methanol system); tR = 5.40 min; identical to the pattern;

TLC: RF identical to reference calcifediol (hexane: ethyl acetate 1: 1).

¹ H NMR (CDCl3) δ: 0.54 (3H, s, 18-CH 3), 0.94 (3H, d, J = 6.0 Hz, 21-CH3), 1.22 (6H, s, 26 , 27-CH3), 3.95 (1H, m, 3-H), 4.82 (1H, d, J = 2.4Hz, 19Z-H), 5.05 (1H, d, J = 2 , 4 Hz, 19E-H), 6.03 (1H, d, J = 11.0 Hz, 7-H), 6.24 (1H, d, J = 11.2 Hz, 6-H);

EI-MS m / z (relative intensity) 400 (16), 382 (6), 271 (15), 253 (19), 136 (85), 118 (100), 59 (26);

HRMS, calcd for C27H44O2: 400.3341, found 400.3324.

Example 4

Preparation of (1S, 3R) - (5Z, 7E) -9,10-secocholesta-5,7,10 (19) -trien-, 3,25-triol (Formula 1b)

A mixture of (3R, 23R) - and (3R, 23S) - (5Z, 7B) -1,3-di-t-butyldimethylsilyl-25-trimethylsilyl-23-phenylsulfonyl-9.10-secocholesta-5,7,10 ( 19) -trien-3,25-triol (30.5 mg, 0.034 mmol, 69%, TLC, system: hexane: ethyl acetate 6: 1, RF = 0.65 and 0.59) was prepared in a similar manner as in the example 1 z (1S, 3R) - (5Z, 7E) -24-phenylsulfonyl-1,3-di- (t-butyldimethylsilyl) -25-trimethylsilyl-9,10-seco-22.23-dinorchola-5,7, 10 (19) -trien-3,25-diol (35.7 mg, 0.049 mmol), after chromatography on silica gel, as a colorless oil. The resulting mixture (30.2 mg, 0.034 mmol) was desulfonylated as described in Example 2 to give (3R) 4-protected after chromatography on silica gel.

PL 190 804 B1

- (5Z, 7E) -1,3-di-t-butyldimethylsilyl-25-trimethylsilyl-9,10-secocholesta-5,7,10 (19) -trien-3,25-diol (3.4 mg, 0.018 mmol, 52.5%) as a colorless oil. Removal of protecting groups as described in Example 3 gave (1S, 3R) - (5Z, 7B) -9,10-secocholesta-5,7,10 (19) -1,3,25-triol (5.5 mg, 0.013 mmol, 75%) as a white powder.

TLC: RF values identical to standard calcitriol (hexane: propanol-2, 2: 1 and 5% H2O in CH3CN);

UV (EtOH) A _max = 265.4 nm, A _min = 228.4 nm;

¹ H NMR (CDC13) δ (ppm): 0.54 (3H, s, 18-CH 3), 0.94 (3H, d, J = 6.0 Hz, 21-CH3), 1.22 (6H, s, 26.27-CH3), 4.23 (1H, m, 3-H), 4.43 (1H, m, 1-H), 5.00 (1H, br s, 19Z-H), 5 , 32 (1H, br s, 19E-H), 6.01 (1H, d, J = 11.3 Hz, 7-H), 6.38 (1H, d, J = 11.2 Hz, 6- H);

EIMS, m / z (relative intensity) 416 (11), 398 (25), 380 (15), 365 (6), 269 (9), 251 (11), 152 (34), 134 (100), 59 (42);

HRMS, calcd for C27H44O3, found 416.3283.

Claims (3)

A method for the preparation of active vitamin D metabolites of the general formula I, in which X is a hydrogen atom or a hydroxyl group, characterized in that the deprotonated alkyl isohexyl ether sulfone of the formula 2, in which R3 is a protecting group such as an alkylsilyl or alkoxyalkyl group having 1 to 6 carbon atoms, is alkylated with the appropriate vitamin tosylate of formula 3, wherein X is H or OR1 and R1 is a protecting group for a hydroxyl function, such as an alkylsilyl or alkoxyalkyl group having 1 to 6 carbon atoms, R1 and R3 are the same or different in the presence of a strong organic base in an aprotic solvent, and the resulting mixture of vitamin sulfones of formula IV, wherein the substituents are as defined above, is desulfonylated with an alkali metal amalgam, preferably sodium amalgam in buffered methanol, followed by removes protecting groups. 2. New vitamin sulfones represented by formula 4, wherein X is H or OR1 and R1 and R3 are the same or different and represent a protecting group such as an alkylsilyl or alkoxyalkyl group containing from 1 to 6 carbon atoms. 3. The cholecalciferol derivatives represented by the formula where X is H or OR1 and R1 and R3 are the same or different and represent a protecting group such as an alkylsilyl or alkoxyalkyl group containing from 1 to 6 carbon atoms.