CA1335105C - 1.alpha.-hydroxyvitamin d2 epimer and derivatives - Google Patents

Abstract

The invention provides a new vitamin D2 compound,.
1a-hydroxy-24-epi-vitamin D2 and certain hydroxy-protected derivatives thereof. The new compound exhibits a distinctive activity pattern comprising high potency in stimulating intestinal calcium transport and little or no activity in inducing bone calcium mobilization or the differentiation of undifferentiated cells in culture, thereby evincing utility in the treatment of diseases characterized by loss of bone mass.

Description

`- 1335105 Novel la-~rdroxyvitamin D2 Epimer and Derivatives This invention relates to vltamin D2 c ,o~Qds, snd more specifically to the preparation of the novel (24S)-epimer of 1~ h~vA~vltam~n D2, and certain terivatives thereof.

Backgrount The natural v~tamin D-derived hormone, 1,25-dihydroxy-v~tamin D3~ and its 25-deoxy analog, la-hydro~yvleamin D3, ~oth e~hibit high activity in vi~o, being known as poeent ~mulators of ehe ineeseinal absorption of ~1 cl and ~he mobilization of cal~ from bone and as effective prolooters of bone calcification. A very similar activity ~attern is shown by 1~,25-dihydroxyvitamin D2 (U.S. Patent 3,880,894~ and its 25-deoxy analog, la-hydro~yvitamin D2 ~U.S. Patent 3,907,843)~
These compounds likew~se elicit the full ~yecL, of vitamln D-type responses such as ineestinal c~ transport, bone aineral mobilizatlon and bone calcification res~onse in the an~m~l or human. Structurally, la,2~-till~d.vA~vitamin D2 and l~-hydLuAyv~tamin D2 are characeerizet by hsving a C-24 stereo~h stry a~ lt occurs in the side chain of ergosterol~
i.e. the~e c ._~nds are defined by the structures shown below~
where R represents ~ide cha~ns (a) and (b), respectively:

.' ~

133510~
-R
~ "` ~ ~, (Q ) o~'~O~s ~0~

More recently the C-24-eplmer of la,~5-dihydroxy~l~amin D~ has been prepared and tested (U.S. Patent 4,588,716 and 4,769tl81).
This compound is charactezized by the structure shown above where R represents side chain (c)~ Remarkably, this ~24-epimerlc vitamin D derlvative exhibits a dlstlnc~ly different biological ac~ivity proflle, in that it ls actlve in stimulating lntestinal calcium absorption and promoting the calclfication of bone, but does not elicit a bone calcium mobilization response~

Dlsclosure of Invention This invention provides a new vitamin D analogue, namely l~-hydroxy-24-epi-vitamin D2, which may be represen~ed by ~he structure below, as well as the acyl and alkylsi]yl derlva~ives of that compound.

C~ .
~J

Thi~ compound~ there~ore9 i8 dis~inguished ~rom the known -1~ h~Lo~v1tamin D2, by having the oppositve me~hyl ~ereor' ~try at C-~4 (i.e~ the 24S-configuration), and lt is urther dist~n~llishpd by exhibiting a strik~ngly di~ferent pattern of biological activley than the known vitamln D2 derivative~ as more fully d~scribed below.
The synthesis of l~-hydroxy-24-epi-vitamin D2 requires the construction of an appropriate side chain unit tlavi1lg ~he desired (S) stereochemistry at the carbon center ~ha~ is to become carbon-24 in the target compound, and the condensation of that side chaln unit w~th a sultable la-hydroxylated vitamltt D nucleu~ so as to generate the desired final product.
The synthcs~s of the optically active side c:hain unit comprised the conversion of commercîally aYailahle t racemic 2,3-dimethylbutanol to the corresponding bromide and ~hen to the I a~esium bromi~e derivative ~1) according ~o published procedures (see T. Suda et al~, J. Am. Chem. Soc. 82, 3396, 1960; ~artin~z et al.~ Gazz. Chim. Ital. 97~ 96, 1967; Organic Synthesis, Collective volume 2, p. 3S8, Wiley ~ Sons, NY~
1943).

The ~ esium bromide derlva~ive ~1~ sho~n below was then rescted with tR)~ toluenesulfinic acld (-)-menthyl ester~
compount ~2) below, under Grignard reaction conditions. Th~s reaction is the key step ,or it pro~ide~ a mix~ure o diaste,. -ric sulfoxides~ namely compounds (~) and (4), whlch ~ay be readily separated by column chrom~togr~phy or by l~i~h presQure liquid chromatography ~plc~ to give both the 2R
~compound 3) and the 2S (compound 4~ stereoicomers.

~h ~ p~7ôl~

,0~ 0 O O
.lol-5 ~ P~ 5 ~ 2s) 1335IO~

Subsequent oxidation of p-tolyl-2~3-dimethylbutyl-sulfoxides 3 and 4 then affords the corresponding optically active sulfones. Thus, as sho~n in the scheme above~ oxidation of sulfoxide (3) with chloroperbenzoir acfd glves the ~2~ -2,3-dlmethylbutyl-p-tolysulfone ~5), whereas anslogous trestment of sulfoxide (4) gives ~2S)-2,3-dimethylbutyl-p-~olysulfone (6).
~ he preced~ng reaction sequence provldes a novel and efficient method for ~he preparation of optically active side chain units as their sulfonyl deriva~ives, which then may be used according to known procedures for the construction of a var~ety of sterold or vltamin D side chains ha~ing a chlral center at C-24. The tolylsulfones (5) and (6) above are new c .~ds; the c~ s.s~o~ding enantiomerlc phenylsulfones have ~een obtained previously by lengthy and elabora~e synthesss ~ori et al.~ Tetrahedron Let~ers 38, 20~g (1982); Sakakibara et al., ~eterocycles 17~ 301 (1982); Ferraboschi and Santaniello, Synth. Commun. 14, 1199 (1984); Koclenski et al., J. Chem. Soc. Perkin Trans. 1, 834 ~1978)].
For the preparation of the desired l~-hydroxy-24-epl-vitamin D2 analogue, the (2S)-2,3-dime~hyl-p-tolylsulfonr (6) as obtained by the above procedure is ~he appropri~te side chain unit~ Accordingly, compound {6) is reacted with the known la-hydroxyvitamin D-22-aldehyde derivatlve (struc~ure 7, below, where Xl and x2 are hydroxy-protec~ing groups~ e.g. an alkylsilyl group, such as t-~utyldimethylsilyl)> using the general procedures of Kutner et al., J~ Org. Chem. 53, 3450 (1988). This condensation yields the side chain aduct represented by structure (8) below (Xl and X2=hydroxy-pro~ect~
ing group), which is then reduced with a metal amalgam to provide the hydroxy-protected 24-epi-vitamin D2 derivative5 structure (g, Xl and X2=hydroxy-protecting groups). Upon .
removal of the hydroxy-protecting groups according ~o standa-d procedures ehere is obtained the de~ired la~hydroxy 24-epi-vitamin D2 ~compound 105 X -X --H)~

~ Q
pl1~5~

X20,~- OX
7 6 :~

- \/ ' Of ~

~ 50~rTo~ ¦

x2~ OX~

c~ Xl x2 o~_p~ g~o~

X~'~o X' 13~5105 -?-As shown by ~he above structures, ~he process of ~hisinvention yields both the free hydroxy compound (~0), where X
and x2 are hydrogen, a~ well as hydroxy-protected derivatives, such as c~ ou~d ~2) . where Xl and x2 represen~ an alkylsilyl group~ Furthermore, the hydroxy compound (10) can be conver~ed to other deri~atives, by the coiresponding 1- and/or 3-acyl derivatives, by standard acylatlon procedures, ~o provide the r~ unds of structure ~9), where Xl and x2 represen~ acyl groups. Alkylsilyl and acyl derivative~ of co~pould (10) ~ind use in applications where enh~nced lipid-solubility is desired~
In this specificatlon and the claims9 tke term talkylsilyl' means a ~rialkylsilicon radical, whe~e each of ~he alkyl groups may have from 1 to 5 carbons in all isomeric fonms. Common examples lnclude trlmethylsilyl~ ~rie~hylsilyl and t-butyldimethylsilyl. The term ~acyl' signlfies an aliphatic acyl group (alkanosyl group) from l to 5 carbons in all isomeric forms (e.g~ formyl, acetyl, propionyl~ e~c.), or an aromatic acyl group, such as ben20yl, or nitro, halo or methyl substituted benzoyl groups.
The proce~ of this inveneion is more particularly described by the following illustrative examples. In the6e examples, designation of products or interme~istes by Arabic numerals, e.g. 1, 2, 3, .~. etc. re~ers to the struc~ures so ,- e~ed in the preceding descrip~ion.

Example l ~2R)-2,3-Dimethylbutyl-p-tolylsulfoxide (3) and (2S)-2,3-dimethyl-p-tolylsulfoxide (4) M~nesium turnings (0~24 g, 10 mmol) and a crys~al o~ I2 were placed in a dry flask and covered with 5.0 mL o~ anhydrous -B-~etrahydrofuran. l-Bromo-2,3-dimethylbutane (1.54 ~, 8 mmol) was added slowly with stirring unter nitrogen atmosphere and occasional cooling. The mixturc was stirred at room ~emperature for 1.5 h or unt~l mo~t of the ma~ncsium ~8S
con~umet. This mixture ~Cont~n~ng compound ~) was cooled and 2.35 g (R)~ p-toluenesulfinic acld ~ menthyl ~stcr ~compound 2) (10 mmol) in 10.0 mL o~ anhydrous tetrahydrofuran w~s added~ The mixturc W2S stirred under nl~roge~l a~mospherc at roo~ temperature for 16 h, cooled and decomposed wi~h saturated NH4Cl solutlon. The organ~c layer was separs~e-d and the squeou~ phase extracted several tlmes wi~h ether. ~l`h~
comb~ned organ~c phase was washed with water and ~rine, dried with MgS04, filtered and evaporaeed. The rcsidue was chromatographæd on a 70-270 mesh sllica gel column to give 1.26 g of diastereomerlc sulfoxide mixture. This was separa~ed ~y flash chromatography on a 230-400 mesh silica gel column wi~h ethyl acetate and hexan~ mixtures or by semiprepara~ive ll~LC
(20rbax Sil, 9.4 x 25 cm column) uslng et~yl ace~e-lexane mixtures. The first compound to elute was the (S)-(-)-p-tolyl-(2R)-2,3-dimethylbutylsulfox~de (3) and ~he second c ou~d wa~ the (S)-(-)-p-tolyl-(2S)-2,3-dimetlly~hutyl sulfoxide (4). MS m/z (relative intensity 224 tM ~ 6)~ 208 (14), 140 (100), 139 (8), 124 (30), 92 (22), ~ 4 (10)~
43 (71), 28 <34), 27 (25); H NMR (CDC13) ~ 0.80 (3H~ d, Ja7~0 Hz), O.B9 (3H, d, J=7.0 Hz), 0.98 (3H, d, J=6.5 Hz), 1.6-1.82 (2H, m), 2.42 (3H, s, CH3-Ar~, 2.71 (2H, m)~ 7~34 (2H, d~ JY15 Hz) (H-aryl ortho), 7.54 (2H, d, Jsl5 Hz, H-aryl or~ho). (2S) sulfoxide 4 l]D = -153.5 (c=4 in CHC13); (2R) sul~oxlde 3 [a]D 2 -444.8 (c=4 in CHC13).

Example 2 (~S)-2,3-Dimethylbu~yl-~-~olylsulfone (6) (2S)-2,3-Dimethylbutyl-p-tolylsulfoxide (4) (52 mg, 0.2 ~mol) wa~ dissolved in 1~0 mL of anhydrous dichloromethane and 60 mg (0.3 mmol) of 3~chlo~operoxybenzolc acid (80-85Z, Sigma) sddet wlth stirrlng. The ~eac~ion mixture wa~ stirred ~or 2 h ~nd q~n~d with lOX sodium bicarbonate. ~ore dichloromethanc was added and ~he comb~ned organic exeracts were washed wi~h aqueous sodium sulfite and br~ne and dried w~th MgS04. Tlle solvent was re ved in vacuo and the crude sulfone was purified by silica gel flash chromatography uslng hexane ethyl aceta~e xtures to afford sulfone ~6) as a coiorleqs oil. For analytlcal purposes thls was also purified by HPLC (~orbax Sil 9.4 x 25 cm column) using lOX ethyl acetaee in hexane to give ~2 mg of pure (2S)-sulfone ~6): [a3D = + 17 tc-3.5 in C1~.13);
MS m/z (relative intensity) 240 ~M , 3), 197 (5), 157 (100)~ 92 ~19), 91 (27), 85 (25)~ 84 ~31), 43 (72); lH NMR ~ 0.77 (3H, d, J-7 Hz), 0.82 (3~, d~ J=7~0 ~z)~ 1.00 ~3H, d, J=7.0 112), 1.66-1.98 (~H, m), 2~45 (3H, s, CH3-Aryl), 2.86 (lH, dd, J=8, 11 Hz), 3.06 ~lH, dd, j=4, 12 Hz), 7.35 (2~, d, J=7.0 l~z, ~-aryl ortho), 7.75 ~2H, d, J=8, H-aryl ortho).

E~ample 3 (2R)-2,3-Dimethylbutyl-p-tolylsulfone (5) The (2R)-sulfone (5) was prepared by oxidation of sulfoxide 3, usin~ the experimental procedure as described ln Example 2 abo~e. The resulting (2R) sulfone (5) showed an optical rotation of ~]20 = _ 19 (c-1.4, CHC13).

-lo~ 133510~
Example 4 la-Hydroxy-24-epi-vitamin D2 ~103 To a stirred 801ution of 30 mg (125 ~mol) of ~2S)-2,3-dimethylbutyl-p-tolylsulfone (6) in 300 ~L anhydrous tetrahydrofurane (containing l.10-phenanthroline as an lndicator) was added under argon at -78C 18 llL (130 ~mol) o~
~iisopropylam~ne followed by ~6 ~L of a solution of n-BuLi in hexane (1.50 M~ 130 ~mol). The solution was stirred at -78C
for 15 min (dark bro~n color), and 4 mg (7 ~mol) of the protected aldehyde t7, Xl-~2=t-BuMe2Si) in 0.3 mL of anhydrous ~etrahydrofurane was added and the mixture stirred ~mder argon at -78 C for 1 h. The reaction mix~ure was quenched with 1 ml of saturated N~4Cl solution, warmed to 0C and ex~racted ~ith ethyl acetate, and the organic phase was wsshed with satura~ed ~aCl. The or~anic phase was dried with MgS04, flltered and evaporated. The residue was redissolved in e~hyl acetate, passed through a Sep Pak column in ethylacetate and evaporated.
The residue was purified by HPLC (Zorbax Sil 9.4 x 2S cm column) using 10% ethylacetate in h~xane to glve 3.3 mg ~587) of the hydroxysulfones (8, X =X2=t-BuMe2Si~. MS m/z (rela~ive intensity) 8.2 ~M , 20), 680 (34), 440 ~52), 248 (64), 157 (65), 75 ~100).
A sa-turated solution of ~a2~P04 in methanol (1.0 m~) was added to a stirred solution of the 3.3 mg sul~one {8) in 1.0 mL
of anhydrous tetrahydrofuran followed by 160 mg o~ po~dered anhydrous Na2HP04. The mixture was stirred under argon for 15 min, cooled to 0C and fresh 5X sodium amalgam (ca. 400 mg) added. The mixture was stirred a~ 5C ~or 20 h; 5 mL of hexane added and the hexane layer decanted. The solid materlal was then extracted with 10~ ethyl acetate ln hexane (3x5 mL). The * Trade-mark - 133~10~

combined organic phase was washed with sa~urated NaCl and filtered through a Sep Pak cartridge snd evapo~ated. Final purification on HP~C (Zosbax Sil 9.4 x 25 cm column) (10% ethyl acetate in hexane as solvent~ gave 1.05 mg (40%) of vitamin D2 terivative (9, Xl=~2=t-~uMe2Si). ~ a byproduc~, 0.47 mg o~
~he 2~-hydroxylated derivative was ~l~o o~tained.) MS m/z ~re~ative {n~ensity) 640 (M 9 ~4), 508 {65), ~.b8 ~67~, 147 ~13), 73 ~100), 6g ~S8~ NMR ~ 0.54 ~3~f s, 18-C~3), 4.19 ~iH, m, 3-H), 4.35 (lH, m, l-H)~ 4.86 ~1~" S, 19Z-H), S.17 ~3H, m, 19~-~ and 22-23-H-S), 6.00 (lH, dr 3=9.6 Hæ~ 7 H~ 6.23 (lHs d, J~8.8 Hz, 6-H). The hydroxy~protected diol (4, 800 llg) was dissolved ~n 0.5 mL of anhydrous tetr~hydro~uran, and to ~is solutfon was ad~ed 90 ~L lM solution of tetrabuty]am~onium fluoride in tetrahytrofuran. The mixture wa~ s~irred under argon at 55 C for 1 h. The mixture was cooled and 5 mL o~
e~her added. The organic phase was wsshed with 6atura~ed NaCl sslution and tried over anhydrou~ Mg~4, evaporated and redissolved in 20Z 2-p~opanol in hexane and fll~ered througl Sep-Pak. Preparative HPLC ~Zorbax-Sil 9.4 mm x 25 c~ column~
ln 20X ~-propanol in hexane gave 308 ~g la-hydroxy-24-epi vitamin D2 (10~ X =X =H). la-Hydroxy-~4-epi-vltamin D2 exhibited the followlng spectral propertie~- UV ~EtOH) A1n~X:
264 nm, Amin 228; MS m/z (relative intensity) 412 ~M , 13), 394 (21), 37~ (7), 287 t4), 269 ~7), 251 ~6~, 252 (31), 251 (6), 152 (35), 151 ~15), 134 (100), 69 (50), 55 (73); lH NMR ~CDC13) ~ 0.49 (3-H, S, 18-CH3)~ 0.77 (3-H, d, Jz7.1 26 or 27-CH3), 0.85 (3H, d, J=6.8, 28-CH3), 0.94 (3H, d, 3=6.5, 21-CH3), 4.94 (lH, S, l9Z-H), 5.13 t2H, m, 22 and 23 H) (5.11, 5.13, 5.14), 5.26 (lH, S, l9E-H), 5.99 (lH, d~ J=11.2 Hz, 7-M)s 6.35 (lH, d, J-11.2 Hz, 6-H), 4.21 (lH, m, 3-H), 4.41 ~lH, m, l-H). la-Hydroxy-24-epi-vitamin D2 can be dlstingulshed from the previously known la-l~yd~ vitamin D2 by reverse phase HPLC
(4.6 mm x 25 cm, ODS-Zorbax co~umn) with 15% water in acetonitrlle. The first comp~und to elute ~n ~his system was ~a-hydroxy-24-epi-vitamin D2 and the second, the known la-hydroxyvltamin D2.

~iological Activlty of la-~droxy-24-cpi-~it~min D2 The ne~ analogue was eested in the vitamin D deficien~
rat. These tests indica~e that la-hydroxy-24-epi-vi~amin D2 ha8 a biological acti~ity spectrum ~hat is distinc~ly differen~
from that of the previously known l-hydroxyvitamin D2~ In Tsble 1 below, representative assay results are given. Th~se inr~llde te~ts of ineestinal calcium transpor~ activity ("S/M
rat~os"), and of bone mlneral mobilization as reflec~ed by serum calcium levels. These assays were conducted accordiug ~o standard procedures ~see e.g~, U.S. Patent 4~5885176). The rats used in these assays were made vitamin D-deficient by maintenance on a ~itamin D-free~ low calcium diet (0.02X Ca, .37~ P) for 3-1/2 weeks. They received the test compounds (or vehicle alone; -D control group) 20 h prior to sacrifice.
The data of Table 1 show that the new analogue~
la-hydroxy-24-epi-vieamin D2 exhibits high activi~y in stimulating ineestinal calcium transport being es~entially equivalent in th~s activity to the known la-hydroxyvitamin ~2 In contrast, the new compound exhibits no activity in mobilizing calcium from bone. Thus the new compound, although structurally closely related to the known la-hydroxyvitamin D2, exhibits a remarkably different activity profile. In stimulating the absorption of calcium, but not its liberation l335lo5 from bone, the new analogue îs highly suitable as a therapeutic agent for the prevention or treatment of phys~olog~cal conditions characterized by the loss of bone mass.

Table l ~nteseinal Calcium Transport and Bone Mobiliz~ion Activ~ty of la-8~,u~vitamin D2 and la-Hydroxy-24 ~i-Vitamin D2 Group Amount Ca Trans~ort Bone Mobilization ~pmol~ S/M Ratio Serum Ca, mg %

-D ~Cont~ol) 0 2~5 ~ 0~35 ~.7 + ~.20 la-~ydroxy-24- 325 4~3 ~ 0.42 3.9 ~ 0~3g epi-vitamin D2650 4.4 + 0.70a 4~1 + 0.23 la-Hydroxy- 325 5~4 + 0~37 5~3 _ O.lS
~itamin D2 Significant difference compared to respective control groups, p < 0.001.
no significant difference compared to control.

The results of Table 1 demonstrate that, in terms of its calcemic action, the novel l~-hydroxy-24-epi-vitam~n D2 exhibits a biological activity spectrum similar to that of the known la,25-dihydroxy-24-epi-vitamin D2. Howevers further tests showed that the new compound is quite dif~erent from the 133~10S

known 24-epi-D2 derivative in its activity in ~nducing the dlfferentiaeion of -lig~nt cells to normal monocyte-macrophages~ Differentiation activity was ~s~ayed using hum~n le~-k~ ~ cells (HL-60 cells), according to two standard ~ests~
namely the nitroblue tetrazolium reduction ~N2T-reduction) and the phagocytosis assays~ and as shown in Table 2, ~he new ~ompound was compared against la,25-dihydroxyvl~amin D3 (a highly potent differentiation ag~nt) and la,~S-~ihydroxy-24-ep~-vltamin D2.
~ he assays were conducted as described by Ostrem et al.
~J~ Biol. Chem. 262? 14164-14171, 1987~ and ~y DeLuca et al.
~U.S. Patent No. 4,717,721)~ The results glven in Table 2 demonstrate that la.25-dihydroxyvieamin D3 standard has, as expected, remarkable HL-60 cell differentfation activity. Even at doses as low as 10 8 M, this compound prod~ced approximately 64-67Z differentlation in the 4-day tr~al period in both the ~BT-reduction and the phagocytosis assay. la ~25-Dihydroxy~24-epi-v~tamin D2 is somewhat less active ~about 5 tlmcs less active than la,25-dlhydroxyvitamin D3 standard~, but also shows very potent activity ln this system, e~g~ better than G~X
differentiation at 5 x 10 8 M and 80X differentlation at a concentration of 10 7 M~ In contras~, l-hydroxy-24-epi-vîtamin D2 possesses little or no cell differentiation activity. At best, only 16-20X differentiation was observed at a concentration of 10 M, and at a concentration of 1-2 x 10 M, where the la,25-dihydroxy-24-epi-vitamin D2 co~pound sllows 40-50%~differentiation, the new analogue does no~ elici~ a significant differentiation response. Thus, la-hydroxy-24-e~i-vltamin D2 has l~ttle or no activlty ln promoting differentiation of promyelocytes to monocytes. These results -lS-show a marked biological differen~e ~etween the present compound and the previously produced 1,2S-dihytroxy-24-epi-vltamin D2.

Table 2 Activ~y of la-a~dfo~-24-Epi-Vitam~n. D~
in ~L-50 Cell D~fferentiat~on X Di~erentiation C~ ,o~n~ Concentration NBT Reduction Phagocy~osls ~M) la,25-~lhy~roxy- 1 x 10 7 87 + 2 ~9 ~ 3 .
~itamin D3 1 x 10 8 64 + 2 67 + 3 1Q, 25-Dihyt.oxy- 1 x 10 80 + 3 81 + 3 ~4-epi-vitamin D2 5 x lo 8 64 + 3 62 ~ 3 2 x 10 ~ 48 + 3 49 ~ Z
1 ~ 10 3 39 ~ 3 40 3 la-~ydroxy-24-epi- 1 x 10 22 + 2 16 ~ 2 vitamin D2 5 x 10 ~ 14 + 2 9 ~ 1 2 x 10 8 6 + 2 6 ~ 3 1 x 10 8 4 ~ 2 4. ~ Z

Thus the p~eceding assays demonstrate that the new compoun~, la-hydroxy-24-epi-vitamin D2 exhibits a distinct and unique spectrum of activities -- namely high potency in stimulating calcium transport, no activity in mobilizing calcium from bone, and litt~e~ if any~ differen~iation activl~y -- which clearly distinguishes the compound from ~hose o~ the prior art.
The new compound, thereLore~ represents a valuable addition to the repertoire of use~ul therapeutic agents, and ~ay be applied advautageously in situations where ~he speciflc stimulation of intestinal calci~tm transport is deslred, e.g~
diseases such as osteotys~rophy or osteoporosis char&cteri~ed by loss of bone mass.
For treatment purposes~ the novel compound of this invention may be ~ormulated as a solution in innocuous soivents~ or as an emulsion, suspen~ion or dispersion in su~table solvents or carriers, or as pills~ tablets or capsules, together with solid carriers, accordlng to conventional methods known in the art~ The compound is advantageously administered by in~ection, or by lntravenous ~nfusion of suitable sterile solutions, or in form o~ llquid o~
solid doses via ~he ~ tary canal. Doses of from 1 ~g to S0 ~g per day of l~-hydroxy-24-epi-vitamin D2 are appropriate for ~reatment purpos~s, such doses being ad~usted according to ~he disease to be treated and the response of the subjec~ as is -~ell understood in the ar~ Since the new compound exhibits specificity o~ action, it is sultably ~ nlstered alone, in situations where only calcium ~ranspor~ sti~lation is d~sired, or together with grad d doses of another active vitamin D
compound -- e~g. la-hydroxyvitamin D2 or D3~ or la,25-dihyd uAyvltamin D3 -- in situations where some degree of bone mineral mobilization (together with calclum transport stimulation) is found to be advantageous.

Claims (4)

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

1. A compound characterized by the structure:

where X1 and X2 are selected from the group consisting of hydrogen, acyl and alkylsllyl.

2. The compound of Claim 1 where X1 and X2 represent hydrogen.

3. A pharmaceutical preparation containing a compound of Claim 1 together with a pharmaceutically acceptable excipient.

4. A pharmaceutical preparation containing the compound of Claim 2 together with a pharmaceutically acceptable excipient.