CA1055015A - Processes for preparation of steroid derivatives - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A process for the preparation of 1a-hydroxycholecal-ciferol characterized by reacting cholesta-1,5,7-trien-3.beta.-ol with a triazoline-3,5-dione to form a 1,4-cyclized adduct thereof, oxidizing the adduct with a peroxide to form the corresponding 1.alpha.,2.alpha.-epoxide, reducing said epoxide to cholesta-5,7-diene-1.alpha.,3.beta.-diol which is then subjected to radiation with ultraviolet rays to give 1.alpha.,3.beta.-dihydroxyprevitamin D3 which is allowed to stand still in the dark thereby producing 1.alpha.-hydroxy-cholecalciferol. The cholesta-1,5,7-trien-3.beta.-ol used as starting material is valuable as an intermediate and is prepared by isomerizing cholesta-1,4,6-trien-3-one in the presence of a basic catalyst and reducing the resulting cholesta-1,5,7-trien-3-one with a metal boron hydride. The 1.alpha.-hydroxycholecalciferol has a much higher vitamin D-like biological activity than vitamin D2 or vitamin D3 and is valuable as a nutrition-promoting agent and as an anti-rachitic agent.

Description

1055~)1S
This invention relates to a process for the preparat.ion Or l~-hydroxycholecalcirerol represented by the following formula (I):

'~1 ~,CH2 H ~ ~ .

In the instant specification Roman numerals denote compounds indicated by the same Roman numerals in the reaction formulae given hereinafter.
According to this invention, l~-hydroxycholecalci-ferol (I) is prepared by reacting cholesta-1,5,7-trien-3~-ol (II) with a triazolone-3,5-dione represented by the following general formula (II'): ~
R~

t~herein Rl stands for an alkyl or aryl group, reacting the resulting triazoline adduct represented by the following general formula (III):

- HO ~ . (III) N / ~ O

0~

10550~5 wherein Rl is as defined above, with a peroxide, reducing the resulting 1,2a-epoxide compound represented by the following general formula ~IV) '~' ~``. ` , ~0 N ~$=o (IV) ~ N
Rl wherein Rl is as defined above, with an alkali metal aluminum hydride, subjecting the resulting cholesta-5,7-diene-la,3~-diol (V) to radiation of ultraviolet rays and allowing the resulting 1,3B-dihydroxyprevitamin D3 (VI) to stand still in the dark.
l~-Hydroxycholecalciferol was found to have much highe~
biological activity than vitamin D2 and vitamin D3, and this compound is very valuable as a nutrition-promoting agent and an anti-rachitic agent.
As the process fvr the synthesis of l~-hydroxychole-calciferol, there-are known the method of DeLuca et al (see Japanese Patent Application Laid-Open Specification No. 62750/73) and the method of Barton et al ~see Journal.of The American Society, 95, p. 2748, 1973). Each of these known methods passes through a diacetyl derivative of 1,3~-dihydroxyprovitamin D3, and in order to form the 5,7-diene atomic group in this inter-mediate compound, in each of these known methods such severe reaction steps as introduction of the bromine atom into the 7-position and subsequent formation of~7'8double bond by dehydrobromination should be performed. At these steps, 2 hydroxyl groups at the la- and 3~-positions should be protected 105~iO~L5 with an acetyl group or the like. Accordingly, this protective group should be split off at the subsequent step. Further, such undesired side reactions as isolation of the la-acetoxy group (axial form) and rearrangement of the double bond in the product are caused to occur simultaneously with the dehydrobromination, and therefore, reduction of the yield cannot be avoided and the produet should be subjected to complicated refining operations.
In the process of this invention, since the 5,7-diene atomie group can be formed under mild eonditions, occurrence of side reaetions sueh as isolation of the hydroxyl group and re-arrangement of the double bond ean be prevented. Further, since it is unnecessary to protect the hydroxyl groups, la-3~-dihydroxy-previtamin~D3 ean be prepared directly without splitting-off of the protective group. In these points, the proeess of this invention is advantageous over the above-mentioned known methods.
The process of this invention eomprises the steps shown by the following reaction formulae:

HO~ H~
II N

~ N
III R

H~ H

0~ \R

IV

lOSS0~5 Q}~ m H ~ >

VI
` /`~/
wherein R stands for an alkyl side chain and Rl is as defined above.
At t.he first step of the process of this inve.~cion, 1 mole of the compound of the formula (II) is reacted wil:h 1 to 3 moles of a triazoline derivative of the formula (II'~ in a solvent. The triazoline derivative of the formula (II') is prepared according to the method disclosed in Chemische Berichte, 100, p. 678 (1967). As thé triazoline derivative, there are _ __ employed, for example, 4-phenyl-1,2,4-triazoline-3,5-dione, 4-(p-tolyl)-1,2,4-triazoline-3,5-dione and 4-methyl-1,2,4-triazoline-3,5-dione. Ordinary organic solvents, for example, benzole and tetrahydrofuran, are used as the solvent.
The so prepared compound of the formula (III) is then oxidized with a peroxide. Good results are obtained when an organic peroxide such as peracetic acid, perbenzoic acid and m-chloroperbenzoic acid is used as the peroxide. The peroxide is used in an amount of 1 to 5 moles per mole of the compound ~III), and chloroform, methylene chloride, tetrahydroruran or the like is used as the solvent for this oxidation reaction. By this oxidation, the 1~,2~-epoxide of the formula (IV) and the 1~,2~-epoxide of the formula (IV~ are formed as products in yields of about 35% and about ~5~, respectively. Both the products are separated and purified by chromatography using a column packed with silica gel.
The so prepared compound of the formula (IV) is reduced with an alkali metal aluminum hydride in a solvent. As the alkali metal aluminum hydride, there can be used, for example, 1055~)1S
lithium aluminum hydride and potassium aluminum hydride. Use of ether and tetrahydrofuran as the solvent ls preferred. The reaction is carried out 50 to 150C , especially 50 to 100C.
The so prepared compound of the formual (V) is sub-jected to radiation of ultraviolet rays in a solvent. Ether, tetrahydrofuran, benzole or the like is used as the solvent.
It is preferred that radiation of ultraviolet rays be conducted at 2 temperat-lre approximating room temperature ~n an inert gas atmo~phere.
The compound of the formula (VI) prepared by radia-tion of ultraviolet rays can be directly fed to the next step without purification. ~hen the compound of the formula (VI) is allowed to stand still in the dark at room temperature in a solvent for several weeks, l~-hydroxycholecalciferol of the forrnula ~I) is obtained.
According to a further aspect of the invention, the cholesta-1,5,7-trien-3~-ol (II) used as starting material for the preparation of l~-hydroxycholecalciferol (I) is prepared - by isomerizing cholesta-1,4,~-trien-3-one (VII) in the presence of a basic catalyst and reducing the resulting cholesta-1,5,7-trien-3-one (VII) with a metal boron hydride.
The process of this aspect of the invention is re-presented by the following reaction formulae: -0~
VII

o~
HO
VII II

The co~pound of the formula (~ to be used ~s the starting compound in the process for the pre~arat~on of cholesta-1,5,7-trien-3~-ol (II) can easily be prepared a,^cording to the method disclosed in Journal of The Organic Che~istry, 15, p. 898 (1950).
At the first step of the process of this invention, the two double bonds located at~ '5 and ~ '7 positions are isomerized to~ ' and ~ 7' positions, respectively, in the presence of a basic catalyst. In practising this step, the compound of the formula (VII) is reacted by an action of a basic catalyst in a solvent such as ether, isopropyl ether, tetra-hydrofuran~dimethylsulfoxide~ tertiary butyl alcohol and mixtures thereof in an inert gas atmosphere. An alkali metal alcoxide such as potassium tertiary butoxide is excellent as the basic catalyst. Further, it is also possible to use an alkali metal acetylide such as lithium acetylide or an ethylenediamine adduct of lithium acetylide in the state suspended in xylene or toluene.
It is preferred that the reaction be carried out at a low temperature, for example, 0 to 20 C. The so prepared compound of the formula (VIII) can be isolated and purified according to customary procedures, and then fed to the next step. However, since the compound of the formula (VIII) is unstable to heat, it is preferred that the compound (VIII) be directly forwarded to the next step ~ithout isolation.

lOS5015 ~t the second step, t~e compound of the formula (VIII) is reduced ~Jith a metal boron hydride in a solvent. As the solvent, there are employed, for example, methanol, ethanol, propanol, tetrahydrofuran and diethyl ether. As the metal boron hydride, there are employed sodium boron hydride, potassium boron hydride, lithium boron hydride, etc It is also possihle to use a mixture of such metal boron hydride ~ith an alkaline earth metal halide such as calcium chloride, calcium bromide, magnesium chloride and magnesium bromide. For instance, good results can be obtained by using sodium boron hydride and calcium chloride in combination. It ~s preferred that the reaction be carried out at a low temperature, for example, O to 20 C. The excessive metal boron hydride is decomposed and then, the product is easily separated and purified according to customary procedures.
Example 1 (1) Preparation of 1,4-cyclized adduct of cholesta-l, 5,7-trien-3~-ol and 4-phenyl-1,2,4-triazoline-3,5-dione:
A solution of 400 mg of cholesta-1,5,7-trien-3~-ol in 30 ml of tetrahydrofuran is cooled with ice, and 190 mg of 4-phenyl-1,2,4-triaZoline-3,5-dione is added little by little to the solution under agitation. The mixture is agitated at room temperature for 1 hour and the solvent is distilled under reduced pressure. The residue is purified by chromatography using a column pac~.ed with silica gel. Fractions eluted with ether-hexane ( 7:3, v/v ) are collected and recrystallization from ether gives 550 mg of a 1,4-cyclized adduct of cholesta-1,5,7-trien-3~-ol and 4-phenyl-1,2,4-triazoline-3,5-dione having a melting point of 178 to 182C.
EtOH
UV spectrum:~ 255 m~ ( E =4300 ) max IR spectrum:~ 34000, 1755, 1700 cm~
max l~Ci5~15 NMR spectrum (~ in CDC13 ):
5li ( 2,7, s, broad ) 1~l ( 3.63, d, J = 8Hz ) lH (3.75, d, J = 8Hz ) 2H ( 11.35~ s ) lH ( 5.05, t, J - 7Hz ) lH ( 6.7, d.d, J = 15 Hz and 8 Hz)

(2) Preparation of 1,4-cyclized adduct of cholesta-5,7-dien-3~-ol-la,2a-epoxide elld 4-phenyl-1,2,4-triazoline-

3,5-dione:
1.25 g of the 1,4-cyclized adduct of cholesta-1,5,7-trien-3~-ol and 4-phenyl-1,2,4-triazoline-3,5-dione is dissolved in 50 ml of chloroform, and 560 mg of m-chloroperbenzoic acid is added to the solution. The mixture is agitated for 20 hours at room temperature, and 200 mg of m-chloroperbenzoic acid is further added and the mixture is agitated again for 20 hours.
The reaction mixture liquid is diluted ~ith chloroform, washed with a 10% aqueous solution of potassium carbonate and dried with magnesium sulfate. Then, the solvent is distilled under reduced pressure. The residue is purified by silica gel chroma-tography, and first effluent fractions eluted with ether are collected, and recrystallization from methanol gives 680 g of a crystal melting at 172 to 173 C. The second ether effluent fractions are collected, and recrystallization from methanol gives 400 mg of a 1,4-cyclized adduct of cholesta-5,7-dien-3~-ol-la,2~-epoxide and 4-phenyl-1,2,4-triazoline-3,5-dlone having a melting point of 152 to 154 C.
IR spectrum:~ 3400, 1750, 1690 cm~
max Mass spectrum: m/e 398, 380, 365, 354, 351, 338 NMR spectrum: ( ~ in CDC13 ):
5H ( 2.8, s, broad) lH ( 3.75, d, J = 8Hz ) lOSSO~S
lH ( 4.0, d, J = 8 Hz ) lH ~ 5.2, m ~
The above compound having a melting point of 172 to 173C. is a 1,4-cyclized adduct of cholesta-5,7-dien-3~-ol-1~,2B-epoxide and 4-phenyl-1,2,4-triazoline-3,5-dione.
XBr 3400, 3215, 1760, 1710 cm 1 IR spectrum: ~
max Mass spectrum: m/e 398, 380, 365, 354, 351, 338 NMr spectrum ( ~ in CDC13 ):

5H l 2.8, s, broad ) 1~ ~ 3.75, d, J = 8Hz ) lH ~ 3.95, d, J = 8H~ ) lH ( 5.15, m ) (3) Preparation of cholesta-5,7-diene-1~,3B-diol:
A solution of 500 mg of the 1,4-cyclized adduct of cholesta-5,7-dien-3~-ol-1~,2a-epoxide and 4-phenyl-1,2,4-triazoline-3,5-dione in 40 ml of tetrahydrofuran is added dropwise under agitation to a solution of 600 mg of lithium aluminum hydride in 30 ml of tetrahydrofuran. Then, the reaction mixture liquid is mildly refluxed and boiled for 1 hour and cooled, and a saturated aqueous solution of sodium sulfate is added to the reaction mixture to decompose excessive lithium aluminum hydride. The organic solvent layer is separated and dried, and the solvent is distilled. The residue is purified by chromatography using a column packed with silica gel. Fractions eluted with ether-hexane ( 7 : 3, v/v ) are collected, and recrystallization from methanol gives 210 mg of cholesta-5,7-diene-1~,3~-diol.
la]D = ~45 ~ as measured in chloroform ) NMR spectrum ( in CDC13 ):

lH ( 4.40, d, J ~ 6Hz~
lH ( 4.73, d, J - 6Hz~

_ g _ 10550~5 lH ( 6.05, m, wl/2 = 25Hz ) lH ( 6.30, m. wl/2 = 8Hz ) Mass spectrum: m/e 400 (M+)~ 382, 364, 341, 326, 312 EtOH
W spectrum: ~ (loge) max 262 ( 3.92 ), 271 ( 4.07 )~ 282 ( 4.11 ), 293.5 ( 3.87 ) m~

(4) Preparation of la, 3~-dihydroxyprevitamin D3.
- A solution of 25 mg of cholesta-5,7-diene-la,3~-diol in 650 ml of ether is subjected to radiation of ultraviolet rays for 14 minutes in an argon gas atmosphere by passing it through a Vycor filter using a 200-W high pressure mercury lamp ( Model 654A-36 manufactured by Hanovia ). The solvent is distilled at room temperature under reduced pressure. This operation is repeated twice, and 50 mg of the so obtained crude product is fractionated by chromatography using a column packed with 20 g of Sephadex LH-20. The first effluent fractions eluted with chloroform-hexane ( 65 : 35, v/v ) give 13.5 mg of oily la,3~-dihydroxyprovitamin D3. The compound exhibits a maximum ultraviolet absorption at 260 m~ in an ether solution.

(5) Preparation of la-hydroxycholecalciferol:
A solution of 13.5 mg of 1~,3~-dihydroxyprevitamin D3 in 200 ml of ether is allowed to stand still in the dark at room temperature in an argon gas atmosphere for 2 weeks. During this period, the position of the maximum ultraviolet a~sorption is shifted from 260 m~ to 264 ~, and the absorption intensity becomes 1.6 times as high as the original intensity~ The sol-vent is distilled at room temperature under reduced pressure, and the residue is purified by chromatography using a column pac~ed with 10 g of Sephadex L~-20. The fractions eluted with chloroform-haxane ( 65 : 35, v/v ) give 6.5 mg of oily la-hydroxycholecalciferol.
~Sass spectru~: m/e 400 (M ), 382, 364, 287, 152, 134 ~OCi501S
rrhe cholesta-1,5,7-trien-3B-ol used as starting material ~s paragraph (1) of Example 1 described above may be prepared as follows:

(6) Preparation of cholesta-1,5,7-trien-3-one:
A reaction vessel is charged with 20 ml of dimethyl-sulfoxide, and a solution of 2 g of cholesta-1,4,6-trien-3-one in 20 ml of ether is added thereto. Then, the inside atmosphere of the reaction vessel is replaced with argon gas. Powdery potassium tertiary butoxide prepared from 1 g of potassium and '0 20 ml of tertiary butanol is added at a time to the above solution under violent agitation and water coQling~ The~reaction mixture liquid is violently agitated for 12 minutes and is poured into ice ~ater saturated with carbon dioxide gas by addition Or d~y ice. Then, the mixture is extracted with 60o ml of a benzole-ethyl acetate mixture ( 1 : 2, v/v ) cooled in advance to 0 to -5C. The extract is promptly ~rashed with a large quantity of ice ~rater until the washing liquid becomes neutral; followed by drying and distillation of the solvent at room temperature under reduced pressure. When 1.6 g of the residue is recrystallized 23 from methanol, 800 mg of cholesta-1,5,7-trien-3-one having a melting point o~ 136 to 146C. is obtained. When this compound is allowed to stand still at room temperature, it graduaIly decomposes.
EtOH EtOH
UV spectrum:~ 230, 268, 277, 288 m~: ~ 251 m~
max min NI~R spectrum t% in CDC13 ):
lH ( 3.25, d, J = 11 Hz ) lH ( 4.2, d, J = 11 Hz ) lH ( 4.42, d, J = 6 Hz ) lH ( 4.63, d, J = 6 Hz ) lH ( 6.6, d, J = 17 Hz ) lH ( 7.07, d, J = 17 Hz ) 10550~5

(7) Preparation of cholesta-1,5,7-trien-3~-ol:
A solution of 250 mg of sodium boron hydride in 20 ml o~ methanol is added drop~ise under agitation to a solution of 500 mg of calcium chloride in 15 ml o~ methanol cooled to -10C.
The mixture is agitated for 20 minutes at a temperature maintained at -10C. Then, a solution of 600 mg of cholesta-1,5,7-trien-3-one in 25 ml of ether is added dropwise to the above liquid mixture under agitation over a period of 20 minutes. The reactio~ mixture liquid is agitated for 1 hour at -10C. and for another 1 hour at 0C. Then, acetone is added to the reaction mixture and the solvent is distilled under reduced pressure. The residue is mixed with water and the mixture is made weakly acidic by addition of acetic acid and extracted with methylene chloride. The extract is washed with water and dried with magnesium sulfate. Methylene chloride is distilled, and the residue is purified by chroma-tography using a column packed with alumina. The fraction eluted with ether-hexane ( 1 : 1, v/v ) is recrystallized from~methanol to obtain 400 mg of cholesta-1,5,7-trien-3~-ol having a melting point of 128 to 129C.

EtOH
UV spectrum: ~ 263, 271, 281, 292 m~
max Mass spectrum: m/e 382 (M~), 364, 349 NMR spectrum: (~ in CDC13 ):
2H ( 4.4, s ) lH ( 4.4, d, J = 6 Hz ) lH ( 4.60, d, J = 5 Hz ) lH ( 5.8, d.d, J = 10 Hz and J = 6 Hz ) ~ KBr IR spectrum ~l 3400, 1620cm~
max The cholesta-1,5,7-trien-3~-ol used as starting material in paragraph (1) of Example 1 described above may also be prepared as follows:

In the sam.e manner as in Example 1-(6), 2 g of cholesta-1,4,6-trien-3-one is isomerized, and the reaction mixture liquid is poured into ice water and extracted with a henzole-ethyl acetate liquid mixture. The extract is dried and the solvent is distilled to obtain 1.6 g of the residue. The residue is directly forwarded to the next reduction step without purification. More specifically, the above residue is dissolved in 30 ml of ether, and the solution ls graduall~ added dropwise at -20C. under agitation to a s~lution of a potassium boron hydride prepared from 500 mg of potas~ium boron hydride, 1 g of calcium chloride and 50 ml of ethar.ol ln the same manner as in Example 1-(7). After completion of the dro3wise addition, the mixture is agitated for 1 hour at -10 to -15C. and for another 1 hour at 0C. Then, the reaction mixture liquid is treated in the same manner as in Example 1-(7) to obtain 550 mg of cholesta-1,5,7-trien-3~-ol having a melting point of 128 to 129 C. When the so obtained product is mixed with the standard substance obtained in Example 1-(7), no lowering of the melting point is observed, and the UV, IR, NMR and mass spectra of both the products are quite in agreement with each other.

Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the preparation of cholesta-1,5,7-trien-3.beta.-ol characterized by isomerizing cholesta-1,4,6-trien-3-one in the presence of a basic catalyst and reducing the re-sulting cholesta-1,5,7-trien-3-one with a metal boron hydride.

2. The process according to claim 1 wherein the isomerizing step is carried out in a solvent in an inert gas atmosphere.

3. The process according to claim 2 wherein the solvent is ether, isopropyl ether, tetrahydrofuran, dimethyl-sulfoxide, tertiary butyl alcohol or a mixture thereof.

4. The process according to claim 2 wherein the inert gas is argon.

5. The process according to claim 1, 2 or 4 wherein the isomerizing step is carried out in a mixture of dimethylsulfoxide and ether in an atmosphere of argon.

6. The process according to claim 1 wherein the basic catalyst is an alkali metal alkoxide, an alkali metal acetylide or an ethylenediamine adduct of an alkali metal acetylide.

7. The process according to claim 6 wherein the alkali metal alkoxide is potassium tertiary butoxide.

8. The process of claim 6 wherein the alkali metal acetylide is lithium acetylide or an ethylenediamine adduct of lithium acetylide.

9. The process of claim 6 or 8 wherein the lithium acetylide or the ethylenediamine adduct thereof is suspended in xylene or toluene.

10. The process of claim 1, 2 or 6 wherein the reaction is carried out at a low temperature.

11. The process of claim 1, 2 or 6 wherein the reaction is carried out at a temperature of about 0° to 20°C.

12. The process of claim 1 wherein the reducing step is carried out by means of a metal boron hydride in a solvent.

13. The process according to claim 12 wherein the solvent is methanol, ethanol, propanol, tetrahydrofuran or diethyl ether or a mixture thereof.

14. The process according to claim 12 or 13 wherein the metal boron hydride is sodium, potassium or lithium boron hydride.

15. The process according to claim 12 wherein the metal boron hydride is used in admixture with an alkaline earth metal halide.

16. The process according to claim 15 wherein the alkaline earth metal halide is calcium chloride, calcium bromide, magnesium chloride or magnesium bromide.

17. The process of claim 12 wherein the metal boron hydride is sodium or potassium boron hydride in admixture with calcium chloride.

18. The process of claim 12, 13 or 17 wherein the reaction is carried out at a low temperature.

19. The process of claim 12, 13 or 17 wherein the reaction is carried out at a temperature of about 0° to 20°C.

20. The process of claim 1 wherein the isomerizing step is carried out using potassium tertiary butoxide in a mix-ture of dimethylsulfoxide and ether as solvent in an argon atmosphere at a temperature of about 0° to 20°C. and the reducing step is carried out using sodium or potassium boron hydride in admixture with calcium chloride in a mixture of methanol and ether or a mixture of ethanol and ether at a temperature of about 0° to 20°c.

21. Cholesta-1,5,7-trien-3.beta.-ol whenever prepared according to the process of claim 1.

22. Cholesta-1,5,7-trien-3.beta.-ol whenever prepared according to the process of claim 20.