GB1574685A

GB1574685A - Vitamin d3 derivatives

Info

Publication number: GB1574685A
Application number: GB11797/78A
Authority: GB
Original assignee: Wisconsin Alumni Research Foundation
Current assignee: Wisconsin Alumni Research Foundation
Priority date: 1977-03-24
Filing date: 1978-03-23
Publication date: 1980-09-10
Also published as: JPS53119858A; DE2812741C2; NL7803154A; DE2812741A1; FR2384755A1; FR2384755B1

Description

(54) VITAMIN D3 DERIVATIVES (71) We, WISCONSIN ALUMNI RESEARCH FOUNDATION, a Corporation organized under the laws of the State of Wisconsin, United States of America, of 614 North Walnut Street, Madison, Wisconsin 53707, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to vitamin D3 derivatives having anti-vitamin D activity.

Still more specifically this invention relates to analogues of vitamin D, which, when co-administered to an animal with vitamin D, will inhibit or abolish the normal response to that animal to vitamin D.

The application of various of the D vitamins to correct certain calcium metabolism disfunctions, e.g. rickets, has long been known. More recently, various derivatives of vitamin D, such as 25 hydroxycholecalciferol (see U.S. Patent No.

3,565,924), 1 a - hydroxycholecalciferol (see U.S. Patent No. 3,741,996) and 1,25 dihydroxycholecalciferol (see U.S. Patent No. 3,697,559) permit the treatment of other metabolic disorders involving calcium and phosphorus balance (imbalance) in animals (see, for example, U.S. Patent Nos.

3,646,203, 3,639,596 and 3,879,548).

Other derivatives of vitamin D have now been found, according to the present invention, which possess anti-vitamin D activity. In other words, such compounds, when co-administered to an animal with vitamin D tend to abolish the normal response of the animal to vitamin D; that is they display an inhibitory action against the intestinal calcium transport and bone calcium mobilization effects of vitamin D.

Such activity is of value in correcting certain calcium disorders in animals such as hypercalcemia, hypervitaminosis D, hypersensitivity to vitamin D and metastatic calcification.

According to the present invention, there is provided a compound having the general formula:

where X is:

wherein each R1 is independently lower alkyl, R2 and R3 are each independently hydrogen, lower acyl, lower alkyl, or aryl and R is hydrogen, acyl having 1 to about 6 carbon atoms or benzoyl.

The terms "lower alkyl" and "lower acyl", as used herein, designate alkyl and acyl substituents, respectively, containing from one to four carbon atoms such as methyl, ethyl and propyl, and acetyl and propionyl, respectively. The aryl substituent is preferably a phenyl or substituted phenyl group.

Since it is commonly known that esterified forms of vitamin D are readily hydrolyzed by esterases within the animal body to the free vitamin (see, for example, Sebrell & Harris, "The Vitamins", Vol. II, Academic Press, N.Y. (1954) p.143) the esters of the present invention are considered to be active in similar manner and are therefore within the scope of the present invention.

It is well established that the biological activity of the D vitamins, and specifically vitamin D2 and D3, depends upon their conversion to the 25-hydroxylated form, this being an obligatory intermediate in the metabolism of the D vitamin in the animal body. Therefore, any agent which can prevent, in vivo, the hydroxylation of the D vitamins at the C-25 position of the molecule would render the vitamins biologically inactive to perform the known vitamin D functions. Although there is no intent to be bound by theoretical considerations, it is believed that the biological properties, i.e. the anti-vitamin D properties, of the compounds of this invention are derived from the inability of the substituent group indicated in the C-25 position (or the position corresponding in a formal sense to the C-25 position) in the molecule, to by hydroxylated by the 25hydroxylase enzyme, the enzyme which normally converts vitamin D to 25-hydroxy vitamin D in the animal body.

The preparation of the compounds of this invention will now be illustrated, purely by way of example, with reference to the compounds in which X represents an aminomethyl radical for example the dimethylaminomethyl compound hereafter referred to as "25 - aza - vitamin Do''. The process can be illustrated with reference to the following reaction scheme: Process Schematic for Preparing 25 - aza vitamin D3

The starting material for this process, namely (20-S)- 6p - methoxy - 20(p toluenesulphonoxymethyl) - 3a,5 - cyclo 5a - pregnane (1) is first halogenated, for example with lithium bromide or iodide.

The resulting halogenated product (2) is then condensed with an appropriate amide, for example dimethylacetamide, in the presence of a strong base to produce the corresponding cholenic acid amide, for example, cholenic acid dimethylamide (3).

This is then acetylated, for example by heating with glacial acetic acid and the acetylated product (4) is then heated with 1,3 - dibromo - 5,5 - dimethyl hydantoin and collidine to produce a mixture of 3p acetoxycholan - 5,7 - and 3p - acetoxycholan - 4,6 - dienoic acid (dimethyl)amides. The 5,7 - diene can be isolated, for example as a Diels - Alder adduct with 4 phenyl - 1,2,4 - triazolin - 3,5 - dione (5).

This can then be reduced with a hydride reducing agent, for example lithium aluminium hydride, to produce the 7dehydrocholesterol (6). Irradiation with ultraviolet light affords the previtamin D3 which can be isolated or directly isomerised to the desired vitamin (7) in the usual way.

These compounds can be readily converted into the corresponding esters with the appropriate acid chloride or acid anhydride, e.g. acetyl chloride or acetic anhydride where the acetic acid ester of the particular compound is desired, in the presence of an organic base.

One skilled in the art will appreciate that the other compounds of this invention can be prepared using analogous methods or modifications thereof. In general the other compounds can be prepared from the bromide intermediate, (2), by reaction with a lithium derivative containing the desired side-chain or a lithium derivative the organic radical of which can be converted into the desired chain, the conversion of the remaining part of the molecule being as described above. In addition the amides can be obtained from compound (4).

The compounds having the formula:

can be prepared by irradiating a compound of the formula:

with ultraviolet light and recovering the desired compound from the irradiated product.

25 - Aza - previtamin D3, for example, can be prepared by irradiating a solution of 25 - aza - 7- dehydrocholesterol with ultraviolet radiation.

The following Example further illustrates the present invention.

(20S) - 6 - Methoxy - 20(p - toluene sulfonoxymethyl)- 3a,5 - cyclo Sa-pregnane (1).

Starting material I was prepared from stigmasterol in overall yield of 61% according to the procedure of J. J. Partride, S. Faber, and M. R. Uskokovic (Helv.

Chim. Acta 57, 764 (1974)). It had the following physical properties: mp 144- 145"; [a]2D=+34 (C98, CHCl3); ir (CCl4) 1190 and 1180 cm-' (sulfonate), 1100 cm-l (C-O for i-ether); nmr (CDCl3) owt7.79 and 7.34 (AB, 4H, JAB=8Hz, tosylate) 3.98 (d of d, J1=9.0, J2=3.4 Hz, 1H, 22E1), 3.78 (d of d, J1=9.0, J2=5.9 Hz, 1H, 22E2), 3.31 (s, 3H, 0 Me), 2.76 (d of d, J1=Jz=2.7 Hz, 1H, 6a-H), 2.45 (s, 3H, tosylate), 1.01 (s. 3H, C-l9), .98 (d, J=6-Hz, 3H, C-21), .68 (s, 3H, C-18), .42 (d of d, J,=7.8, J2=4.8 Hz, 1H, C-4a; mass spectrum m/e (rel. intensity) 500 (M+, 19), 485 (12), 468 (68), 445 (21), 296 (45), 281) (28), 91 (100); homogeneous on tlc (R,=.50, 20% ethyl acetate in Skellysolve B).

(20-S) - 20 - Bromomethyl - 6p methoxy - 3a - 5 - cyclo - 5a - pregnane (2).

2.30 grams of the tosylate 01), in 314 ml acetonitrile, and 3.51 g of dry, powdered lithium bromide was heated at reflux for 6.5 hr. After removal of the solvent by flash evaporation, the solids were dissolved in 150 ml H2O and extracted three times with 50 ml each of dichloromethane. The combined extracts were washed twice with 50 ml H2O, once with 50 ml saturated salt, dried over sodium sulfate and flash evaporated.

Crystallization from aqueous ethanol gave 1.88 g (85%) of2: mp 63.5--650; [a]2D=+55 (C 1.60, CHCl3); ir (CCl4) 1100 cam~' (C-O for i-ether); nmr (CDCl3) a 3.52 (d of d, J1=9 8. J2=2.8 Hz, 1H, C-22E1) 3.34 (d of d, J1=9.8. J2=5.4 Hz, 1H, C-22E2), 3.32 (s, 3H, O-Me), 2.77 (d of d, J1=J2=2.9 Hz, 1H, C6a), 1.09 (d, J=6.3 Hz, 3H, C-21), 1.02 (s, 3H, C-19, .75 (s, 3H, C-18, .68 (d of d, J1=7 9. J2=4.0 Hz, 1H, C-4p), .43 (d of d, J1=7-9. J2=5.0 Hz, 1H, C-4zr); mass spectrum, m/e (rel. intensity) 410 (52, 408 (48), 395 (40), 393 (42), 378 (98), 376 (100), 355 (78), 353 (85); homogeneous on tIc (Rt=70, 100/, ethyl acetate in Skellysolve B); 98% pure by glc (tr=4.1 min); Anal. calcd. for C23H37OBr: C, 67.47; H, 9.11. Found: C, 67.49; H, 9.23.

6 - Methoxy - 3a,5 - cyclo - 5a - cholanic acid dimethylamide (3).

4.9 ml of 1.79 M n-butyl lithium was added to a dry flask charged with 14.5 ml tetrahydrofuran, 3.6 ml hexane, and 1.55 diisopropylamine. The mixture was maintained under N2 at 0 C for .5 hours after which the flask was cooled to -780C, 1.63 ml dimethylacetamide was added, and the mixture was stirred at -780C for 1.25 hours. The bromide (2, 1.2 g in 15 ml tetrahydrofuran) was added, and the mixture stirred at 0 C for 21 hours. After adding a few chips of ice followed by 50 ml 5% HCI, the mixture was extracted three times with dichloromethane (50 ml for each extraction). The organic extracts were combined and washed with saturated salt, dried over sodium sulfate and flash evaporated. The residue was chromatographed on a 250 g column of silica gel. Elution with ethyl acetate afforded (pool tubes 34 to 67, 15 ml fractions) .85 g (70%) of 3 as a clear oil, which resisted crystallization. The oil showed: ir (CCl4) 1655 cm-' (amide, 1100 cm-' (C-O of iether); nmr (CDCl3) a 3.32 (s, 3H, O-Me), 3.00 (s, 3H, N-Me), 2.93 (s, 3H, N-me), 2.77 (d of d, J1=J2=2.9 Hz, 1H, C-6a), 1.02 (s, 3H, C-l9), .94 (d, J=5.9 Hz, 3H, C-21), .72 (s, 3H, C-18, .43 (d of d, J1=8-3. J2=4.8 Hz, 1H, C-4a); mass spectrum m/e (rel.

intensity) 415 (M+, 6), 400 (7), 383 (26), 368 (8), 360 (13), 100 (32), 87 (100); high resolution mass spectrum; Calcd. for C27H95NO2: 415.345; Found: 415.343.

3p - Acetoxy - 5 - cholenic acid dimethyl amide (4).

1.86 g of the cyclosteroid (3) was dissolved in 75 ml glacial acetic acid and the mixture then heated to 70 C for 18 hours.

After cooling to room temperature the mixture was neutralized with 10% aqueous sodium hydroxide and extracted three times with ethyl acetate (100 ml for each extraction). The organic extracts were combined and washed three times with 10% aqueous sodium hydroxide (50 ml for each washing), once with 50 ml of water and once with 50 ml of saturated salt. Flash evaporation gave an amorphous solid that was crystallized from hexane to provide 1.85 g (93 /" of 4: mp 192-193.4 ; [a]%O=41o (c 1.1, CHCl3); ir (CCl4) 1733 and 1245 cm-' (acetate), 1651 cm-' (amide); nmr (CDCl3 a 5.37 (m, 1H, C-6), 4.62 (m, W1,2=20 hz, lH,C- 3α) 3.00 (s, 3H, N-Me), 2.93 (s, 3H, N Me), 2.03 (s, 3H, acetate), 1.02 (s, 3H, C-19), .95 (d, J=5.9 Hz, 3H, C-21), .68 (s, 3H, C18); mass spectrum, m/e (rel. intensity) 443 (M+, .8), 428 (.6), 383 (65), 368 (6), 100 (70), 87 (100); homogeneous on tlc (R=.55, ethyl acetate); 96 /n pure by glc (tR=28.6 min); Anal. Calcd. for C28H45NO3: C, 75.80; H, 10.22; N, 3.16. Found: C, 75.70; H, 10.30; N, 3.09.

4 - Phenyl - 1,2,4 - triazolin - 3,5 - dione adduct of 3p - acetoxycholan - 5,7 dienoic acid dimethyl amide (5).

A mixture of 500 mg of the amide 4, 45 ml carbon tetrachloride, 665 mg sodium bicarbonate and 194 mg 1,3 - dibromo 5,5 - dimethylhydantoin was refluxed under nitrogen for 3 hours. After cooling to OOC, the solid hydantoin was removed by filtration. The filtrate was evaporated, redissolved in 5 ml xylene and added dropwise to a mixture of 300 mg collidine in 65 ml xylene at 1400C. The reaction mixture was maintained at this temperature under N2 for 1.5 hours, cooled to room temperature, diluted with 100 ml benzene, and washed with 50 ml each of 5% HCI, 4% NaHCO3 and saturated salt (NaCI) solution.

After drying over Na2SO4 the solvent was evaporated at reduced pressure and the resulting oil was crystallized with 5.0 ml acetone. The resulting crystals, representing both 4,6 and 5,7-dienes, were dissolved in 50 ml ethyl acetate, cooled to OOC, and titrated with 10.5 ml of a 2 mg/ml solution of 4 phenyl - 1,2,4 - triazolin - 3,5 - dione in ethyl acetate. After removing the solvent by evaporation the residue was purified by preparative tIc developed with 3% MeOH in CHCl3. Crystallization from hexane provided 87 mg (13%) of 5: [α]D20=-77 (C.49, CHCl3); uv (EtOH) Amax 255 nm E3.900); ir (CCI4 1736 and 1242 cm-' (acetate), 1757 and 1705 cm-l (triazoline) 1652 cm-' (amide); nmr (CDCl3) a 7.39 (M, 5H, phenyl), 6.92 and 6.22 (AB, J=8Hz, 2H, C-6 and C-7), 5.42 (t oft, J i=10, J2=5 Hz, 1H, C-3a), 3.28 (d of d, J1=13, J2=5 Hz, 1H, C 4a), 3.00 (s, 3H, N-Me), 2.93 (s, 3H, N Me), 2.01 (s, 3H, acetate, .98 (s, 3H, C-l9), .95 (d, J=5 Hz, 3H, C-21), .81 (s, 3H, C-18); mass spectrum m/e (rel. intensity) 439 (2), 381 (35), 366 (35), 311 (11), 177 (22), 100 (33), 87 (100); homogeneous on tlc (Rf=.53, 3 /,, MeOH in CHCl3).

25 - aza - 7 - dehydrocholesterol (6).

76 mg of lithium aluminium hydride was added to a mixture of 61,1 mg of the adduct (5) in 13 ml dry distilled tetrahydrofuran.

After refluxing under N2 for 7.0 hours, the reaction was terminated by the addition of 5.0 ml of water. The resulting white precipitate was removed by filtration and washed with dichloromethane; 20 ml of water was added to the filtrate to produce a two-phase system. The organic (lower) layer was removed and the aqueous phase was extracted three times with dichloromethane (20 ml for each extraction). The organic extracts were combined and dried over Na2SO4, the solvents were removed at reduced pressure, and the residue was chromatographed on 75 g of aluminium oxide. Elution with 3% MeOH in CHCI3 gave (in tubes 23 to 34, 3.5 ml fractions) an amorphous solid which, after recrystallization from hexane, provided 32 mg (84 /n) of 6: mp 141.5-143 ; [tZ]2g=118 (C. 27, CHCI3; uv (EtOH) Amax 252 nm (E4,500), 262 (E8,100), 271 (E11,300), 281 (11,400), 291 (6,400); ir (CHCl3) 3630 cm-' (OH), 2820 and 2780 and 1460 cm-' (R N-(CH3)2), 1600 and 1655 cm-' diene), 1040 and 1020 cm-' (C-O); nmr (CDCl3) a 5.57 (d of d, J1=5.9, J2=2.4 Hz, 1H, C-6), 5.39) (d of t, J1=5.8, J2=2.1 Hz, 1H, C-7), 3.64 (t oft, J,=ll.l, J2=4.1 Hz, 1H, C-3a), 2.24 (s, 6H, N-(Me)2), .95 (d, J=6Hz, 3H, C-21j, .94 (s, 3H, C-l9), .62 (s, 3H, C-18); mass spectrum m/e (rel. intensity) 385 (M+, 26), 370 (5), 352 (2), 84 (5), 71(4), 58 (100) homogeneous on tlc (R.64. 3% MeOH in CHCIa, aluminium oxide G); 98 /n pure by glc (tR=12.4 min, oven=2600); Anal. Calcd for C26H43NO; C, 80.98; H, 11.24; N, 3.63.

Found: C, 80.81; H, 11.45; N, 3.58; high resolution mass spectrum; Calcd. for C2GH43NO: 385.3345, Found: 385.3350.

25 - Azavitamin D3 (7).

The diene 6 (10.0 mg in 100 ml ethyl ether), in an ice bath, was irradiated under N2 for 3.25 min with vigorous stirring using a water-cooled quartz irradiation apparatus, and a low pressure mercury arc lamp with a "Vycor" (Registered Trade Mark) filter.

The solvent was evaporated, and the residue was purified on a 45 g column of "Sephadex" (Registered Trade Mark) LH20 using MeOH as eluent. (Sephadex LH-20 is a hydroxypropyl ether derivative of a polydextran marketed by Pharmacia Fine Chemicals Inc., Piscataway, N.J.). The previtamin derivative (#max 262) eluted in fractions 37 to 52 (6.5 ml fractions). These fractions were pooled, the solvent was evaporated and the resulting solid was redissolved in 2.0 ml ethanol. After heating to 700C under N2 for 2.0 hours, the sample was applied to the same Sephadex LH-20 column and developed with MeOH.

Fractions 45 to 72 were pooled providing 2.3 mg (23 / > ) of the desired 25 - aza - vitamin D3 (7) as an oil: uv (EtOH) Amax 265 nm, Amin 230 nm; nmr (CDCl3) a 6.24 and 6.03 (AB, J=10.9 Hz, 2H, C-6 and C-7), 5.05 (d of t, J1=2, J2=l Hz, 1H, C-l9), 4.82 (d, J-2 Hz, 1H, C-19), 3.95 (t oft, J1=7.4. J2=3.7 Hz, 1H, C-3), 2.58 (d of d, J1=12, J2=3.4 Hz, 1H, C4a), 2.41 (d of d of d, J1=14, J2=7.1, J3=4.9 Hz, lH, C-la), 2.31 (s, 6H, N-Me)2), 2.29 (d of d, J1=12, J2=7.5 Hz, 1H, C-4-jB), .93 (d, J=6Hz, 3H, C-21), .54 (s, 3H, C-18); mass spectrum m/e (rel. intensity) 385 (M+, 15), 370 (3), 352 (1), 249 (1), 84 (10), 71(4), 58 (100); high resolution mass spectrum; Calcd.

for C26H43NO: 385.3345; Found; 385.3340; homogeneous on tlc (R,=.69, 3% MeOH/CHCI3, Aluminium oxide G); > 99% pure by glc (tr=9.6 and 10.5 min for pyro and isopyro derivatives at a column temperature of 260 C.).

The 25 - aza - vitamin D2 can be readily obtained in crystalline form by dissolving the recovered oil in suitable solvent media such as an ether/hexane mixture and evaporating the solvent from the resulting solution.

Biological Activity of 25 - aza - vitamin D2 The biological properties of 25 - aza vitamin D2 were assayed in a rat using the following experimental protocol: Male albino weanling rats were housed in overhanging wire cages and fed ad libitum a vitamin D-deficient diet (per Suda et al, J.

Nutr. 100, 1049-1052 (1970)) containing 0.02% calcium and 0.3"/, phosphorus for two weeks. The rats were then divided randomly into four groups and dosed intrajugularly as indicated in the Table below. The doses administered were 0.05 ml of ethanol or the indicated material in 0.05 ml of ethanol. The second dose was administered two hours after the first dose. Twenty hours after the second dose the rats were sacrificed and calcium transport and serum calcium levels were determined by the methods described in Blunt et al, Nat'l. Acad. Sci. U.S. 61, 1503 (1968).

TABLE I Experi- Calcium transport Serum Calcium ment Dose 1 Dose 2 ratio + SE (# rats) mg% # SE (# rats) ethanol ethanol 2.4+.1 (7) 4.6+.1 (7) 2 ethanol SOng D3 4.0#.1 (8) 5.6+.1 (8) 3 50,ug25-aza-D3 50 ng U2 2.7+.2(4) 5.0+2(4) 4 ethanol 50yg25-aza-D3 1.5+.1 (4) 4.4+.1 (4) Experiment I represents the control experiment (treatment with solvent only).

Experiment 2 establishes that vitamin D,, given alone produces the expected biological response. Experiment 3 establishes that pretreatment of animals with 25 - aza - vitamin D3 completely suppresses their biological response to vitamin D3. Experiment 4 shows that 25 - aza - vitamin D3 itself does not elicit a vitamin D like response and may have antagonized remaining endogenous vitamin D3.

It is evident from the foregoing data that 25 - aza - vitamin D3 exhibits an anti vitamin D effect and can thus be used to advantage to reduce or reverse the biological effect of the D vitamins or to counteract hypercalcemia. Inasmuch as the other compounds of this invention, which are structurally similar to 25 - aza - vitamin D3, can inhibit or prevent hydroxylation of the D vitamin molecules at the C-25 position (or the position corresponding in a formal sense to C-25), such compounds will, or would be expected to, exhibit anti vitamin D activity.

The compounds of the present invention can accordingly be used whenever antivitamin D activity is required in the forms of admlnlstratlon conventionally useo.

Accordingly the present invention also provides a pharmaceutical composition which comprises a compound of the present invention and a pharmaceutically acceptable diluent or carrier.

WHAT WE CLAIM IS: 1. A compound having the formula:

-in which X represents:

in which R represents hydrogen, an acyl group having from I to 6 carbon atoms or benzoyl, each R1 represents lower alkyl (as hereinbefore defined) and R2 and R3 independently represent hydrogen, lower alkyl, lower acyl (as hereinbefore defined) or aryl.

2. A compound according to claim 1 wherein X is

3. A compound according to claim 2 wherein R is hydrogen and each of R2 and R3.are methyl.

4. A compound according to claim 3, in crystalline form.

5. A process for preparing a compound as claimed in claim 3 or 4 which comprises: halogenating (20-S)- 6p - methoxy 20(p - toluene sulphonoxymethyl) - 3a,5 cyclo - 5a - pregnane (1); condensing the resulting halogenated product with dimethylacetamide in the presence of- a strong base to produce the corresponding cholenic acid dimethylamide; acetylating the resulting condensation proauct; treating the acetylated cholenic acid dimethylamide consecutively with 1,3 dibromo - 5,5 - dimethyl - hydantoin and collidine and recovering the resulting crystalline product comprising a mixture of 3p- - acetoxycholan - 5,7 - and 3p - acetoxycholan - 4,6 - dienoic acid dimethyl amides; isolating the 5,7 - diene compound as a Diels-Alder adduct with 4 - phenyl - 1,2,4 triazolin - - 3,5 - dione; reducing the adduct with a hydride reducing agent and recovering 25. aza - 7 - dehydrocholesterol; subjecting the said 25 - aza

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Experiment I represents the control experiment (treatment with solvent only).

Experiment 2 establishes that vitamin D,, given alone produces the expected biological response. Experiment 3 establishes that pretreatment of animals with 25 - aza - vitamin D3 completely suppresses their biological response to vitamin D3. Experiment 4 shows that 25 - aza - vitamin D3 itself does not elicit a vitamin D like response and may have antagonized remaining endogenous vitamin D3.

It is evident from the foregoing data that

25 - aza - vitamin D3 exhibits an anti vitamin D effect and can thus be used to advantage to reduce or reverse the biological effect of the D vitamins or to counteract hypercalcemia. Inasmuch as the other compounds of this invention, which are structurally similar to 25 - aza - vitamin D3, can inhibit or prevent hydroxylation of the D vitamin molecules at the C-25 position (or the position corresponding in a formal sense to C-25), such compounds will, or would be expected to, exhibit anti vitamin D activity.

The compounds of the present invention can accordingly be used whenever antivitamin D activity is required in the forms of admlnlstratlon conventionally useo.

Accordingly the present invention also provides a pharmaceutical composition which comprises a compound of the present invention and a pharmaceutically acceptable diluent or carrier.

WHAT WE CLAIM IS: 1. A compound having the formula:

-in which X represents:

in which R represents hydrogen, an acyl group having from I to 6 carbon atoms or benzoyl, each R1 represents lower alkyl (as hereinbefore defined) and R2 and R3 independently represent hydrogen, lower alkyl, lower acyl (as hereinbefore defined) or aryl.
2. A compound according to claim 1 wherein X is
3. A compound according to claim 2 wherein R is hydrogen and each of R2 and R3.are methyl.
4. A compound according to claim 3, in crystalline form.
5. A process for preparing a compound as claimed in claim 3 or 4 which comprises: halogenating (20-S)- 6p - methoxy 20(p - toluene sulphonoxymethyl) - 3a,5 cyclo - 5a - pregnane (1); condensing the resulting halogenated product with dimethylacetamide in the presence of- a strong base to produce the corresponding cholenic acid dimethylamide; acetylating the resulting condensation proauct; treating the acetylated cholenic acid dimethylamide consecutively with 1,3 dibromo - 5,5 - dimethyl - hydantoin and collidine and recovering the resulting crystalline product comprising a mixture of 3p- - acetoxycholan - 5,7 - and 3p - acetoxycholan - 4,6 - dienoic acid dimethyl amides; isolating the 5,7 - diene compound as a Diels-Alder adduct with 4 - phenyl - 1,2,4 triazolin - -Ç3,5 - dione; reducing the adduct with a hydride reducing agent and recovering 25. aza - 7 - dehydrocholesterol; subjecting the said 25 - aza

7 - dehydrocholesterol to ultraviolet irradiation and recovering 25 - aza - previtamin D3; and isomerizing the said previtamin to the desired vitamin D3 and, if desired, acylating the vitamin with an acid chloride or acid anhydride.
6. A process according to claim 5 substantially as described in the Example.
7. A comp6und as defined in claim 3 or 4 whenever prepared by a process as claimed in claim 5 or 6.
8. 25 - Aza- 7 - dehydrocholesterol.
9. 25 - Aza - previtamin D3.
10. A process for preparing a compound having the formula:

where R, R2 and R3 are as defined in claim 1 which comprises irradiating a compound having the formula:

with ultraviolet light and recovering the desired compound from the irradiated product.
11. A process for preparing 25 - aza previtamin D3 which comprises irradiating a solution of 25 - aza - 7 - dehydrocholesterol with ultraviolet light and recovering 25 - aza - previtamin D3 from the irradiated product.
12. A compound of formula (X) whenever prepared by a process as claimed in claim 10.
13. 25 - Aza - previtamin D3 whenever prepared by a process as claimed in claim 11.
14. A pharmaceutical composition which comprises at least one compound as claimed in any one of claims 1 to 4 and 7 and a pharmaceutically acceptable carrier or diluent.
15. A method of treating a calcium disorder in a non-human animal which comprises administering a compound as claimed in any one of claims 1 to 4 and 7 or a composition as claimed in claim 14.