Abstract:
Novel 6-bromo derivatives of cholesterol have the formula ##STR1## Such compounds are prepared from the known 6-iodocholesterol by treatment with cuprous bromide.These compounds, labelled with radioisotopes of Br-82 or Br-77, are localized in the adrenal, mammary and ovary tissue of female mammals and in the adrenal or prostate tissue of males when administered to such individuals. This provides a method for imaging adrenal, ovary or prostate tissue which is superior to use of the prior art 6-iodo-cholesterol.

Description:
BACKGROUND OF THE INVENTION 
     There have been reports in the scientific literature concerning the preparation of 6-iodocholesterol, radiolabelled 6-iodocholesterol and the use of such compounds in organ visualization of mammals. For example, the article &#34;Labeling of 6-iodocholesterol with I-131&#34; BO-Li, 3rd Int. Symp. Radiochem. St. Louis, 1980 p. 112 describes the preparation of 6-iodocholesterol labelled with I-131. The article &#34;I-6-iodocholesterol, An Agent for Imaging the Adrenal Gland&#34;, Jixaio and Rursen, Chinese Med. Jour. 62, 237 (1979) describes the preparation of radiolabelled 6-iodocholesterol and its use as as agent which concentrates in the adrenal glands of mammals is of utility in the diagnostic investigation of adrenal gland function. 
     DESCRIPTION OF THE INVENTION 
     The present invention provides in one aspect novel 6-bromo derivatives of cholesterol and especially 6-bromocholesterol of the formula: ##STR2## wherein R=Hydrogen or lower alkanoyl. 
     The invention includes compounds of the above formula and, in addition, such compounds labelled with radioactive isotopes of  77  Br or  82  Br. The inactive compounds are useful aids in determining the properties of the radioactive derivatives. 
     The present invention also includes a method of investigating body functions of a mammal which comprises introducing into the body of a live mammal an amount of 6-bromocholesterol labelled with  77  Br or  82  Br, allowing the labelled bromo compund to be localized in the mammal and then observing the radiation emitted by the labelled bromo cholesterol. 
     In the instance of 6-bromocholesterol it is observed that when the compound is labelled with  77  Br or  82  Br isotopes and administered to mammals and allowed to be absorbed, that the labelled 6-bromocholesterol concentrates in the adrenals mammary and ovaries of female mammals and in the adrenals and prostates of male mammals. The dosage administered to mammals is usually in the range of 0.001-0.1 m Ci/Kg of body weight. The method of introducing the 6-bromocholesterol into the mammal is the same as that used for other radiolabelled steroids and may be introduced by intravenous, intramuscular or oral administration since the ultimate localization of labelled compound is believed to be virtually independent of the route of administration. 
     The 6-bromocholesterol compound or the corresponding derivative labelled with  77  Br or  82  Br is prepared by the following procedure. 
     The known 6-iodo cholesterol is treated in solution with at least an equimolar or preferably a large molar excess of cuprous bromide optionally labelled with  82  Br or  77  Br. The reaction is carried out in a solvent for the steroid, e.g., dimethyl formamide and is stirred at 25° C. for a period of 10-20 hours. The resulting 6-bromocholesterol is isolated from the resulting reaction mixture by dilution with water and extraction with chloroform. The resulting extract of product is evaporated to leave the bromocholesterol as a residue. The residue is purified by recrystallization, preferably from ethanol. If desired the 3-hydroxyl group is acylated to produce a 3-alkanoyl-6-bromo-cholesterol by treating the unacylated compound with at least one equivalent of an anhydride of an aliphatic carboxylic acid for example acetic, propionic or butyric anhydride and recovering the 3-alkanoyloxy-6-bromo-cholesterol produced. 
    
    
     The following examples are illustrative of our invention: 
     EXAMPLE I 
     A. The Synthesis of 6-Bromocholesterol 
     Cuprous Bromide (dried at 120° C., 40 mm Hg)(1.44 g., 10 mmoles) was added to a solution of 6-iodocholesterol* (512 mg, 1 mmole) in dry dimethylformamide (10 ml). The mixture was stirred at room temperature for 16 hours and then filtered to remove solids. The solution was diluted with 5% aqueous Na 2  S 2  O 7  (100 ml) and extracted with chloroform (3×20 ml). The chloroform extracts were dried over MgSO and concentrated in vacuo to give an off white residue. Recrystallization from 95% ethanol gave 6-bromocholesterol as colorless needles. Yield 460 mg (99% of theoretical). M.p. 155° C. 
    
     B. The Structure of 6-Bromocholesterol 
     The structural identity of the material prepared above was rigorously determined by C-13 magnetic resonance spectroscopy and proton magnetic resonance spectroscopy. 
       13  CMR (CDCl 3 , 50.32 MH z , amb): 138.5(S, C-5) 120.6(S,c-6), 70.6(d, c-3), 56.3 and 56.0(2d, c-14 and c-17), 49.7(d, c-9), 43.5 (t, c-4), 42.4(S, c-13), 40.5(S, c-10) 40.1 and 39.5 and 39.4(3t, c-7, c=12 and c-24), 37.2(t, c-1), 36.2 (t, c-22), 35.8(d, c-20), 34.2(3, c-8), 31.2(t, c-2), 28.2(t, c-16), 28.0 (d, c-25), 24.1(t, c-15), 23.9(t, c-23), 22.8 and 22.6(2q, c-26 and c-27), 21.2 (t, c-11), 19.6(q, c-19), 18.7(q, c-21), 11.8(q, c-18). 
     PMR (CDCl 3 , 400 MH z , amb): 83.59(M, 1H, C 3  H--OH. J 3a2a  =12, J 3a2e  =5.2, J 3a4a  =12, J 3a4e  =5.0), 83.2(d of d, 1H, C 4  He, J 4e  7 e  =2.0, J 4e4a  =14.7), 82.5(d of d of d, 1H, C 7  He, J 7e7a  =18.5, J 7e8a  =5.5, J 7e4e  =2.0). 
     Mass Spectroscopy (70 ev, 140° C.): 466, 464(M+, 9%), 387(34%), 386(99%), 368(41%), 352(14%), 249(12%). This evidence serves to confirm the structure of 6-bromocholesterol. 
     EXAMPLE II 
     The Labelling of 6-Bromocholesterol 
     A.  77  Br, 6-Bromocholesterol 
     Na 77  Br (ex MRC, Hammersmith, Init. S.A.=1 mCi/mg, 0.5 mCi), 6-iodocholesterol (1 mg, 0.002 mmoles) and cuprous iodide (1 mgm) in dry dimethylformamide (DMF) was heated at 120° C. for 8 hours. The DMF was removed in vacuo and the residue triturated with 3×1 ml of chloroform. The combined chloroform extracts were chromatographed on silica gel (50 g), using chloroform as solvent to give  77  Br-6-Bromocholesterol as a single radioactive peak. Radiochemical yield 45%. 
     B.  82  Br, 6-Bromocholesterol 
     Cu 82  Br (ex UASF, Init. S.A.=0.8 mCi/mg, 8 mCi) and 6-iodocholesterol (4 mg, 0.008 mmoles) in dry DMF was heated at 120° C. for 16 hours. The DMF was removed in vacuo and the residue triturated with 3×1 ml of chloroform. The combined chloroform extracts were passed through a microcolumn of silica gel (20 mg) using chloroform as solvent. The entire eluate was evaporated to give the  82  Br, 6-bromocholesterol as a colorless crystalline residue. Yield 3.6 mg (100% of theory). 
     EXAMPLE 3 
     Tissue Distribution of Labelled 6-Bromocholesterol 
     The tissue distribution measured as concentration of organ concentration/blood concentration were studied in male and female rats of the istar Strain. The selected compound was administered in solution either intravenously or orally and the animals sacrificed and dissected on the 5th day after dosing. 
     A. Compound of Example 1 
       77  Br 6-Bromocholesterol, via femoral vein injection in 1 male and 1 female rat after 5 days. 
     
         ______________________________________Organ/blood          Male      Female______________________________________liver            1.425       1.537kidney           1.017       1.043spleen           2.212       2.239heart            1.004       0.989lung             2.937       3.687GIT              0.594       0.705pancreas         0.641       0.435blood            1.000       1.000fat              0.932       0.330adrenals         24.306      46.957mammaries        --          2.86ovaries          --          2.18bladder          1.306       1.38muscle           0.467       0.54skin             1.192       1.15uterus           --          0.829testes           0.410       --prostate         14.860      --seminal vesicles 0.520       --______________________________________ 
    
     B. Compound of Example 2 
     
         ______________________________________BR-82,6BROMOCHOLESTROLIN RATS VIA ORAL INJECTIONAFTER 5 DAYSFEMALE            MALEORGAN      ORG/BL     ORGAN      ORG/BL______________________________________Blood      1.00       Blood      1.00Liver      0.62       Liver      0.92Kidney     0.89       Kidney     0.99Spleen     2.06       Spleen     1.66Heart      1.27       Heart      1.11Lung       11.18      Lung       6.77GIT        0.55       GIT        0.85Pancreas   0.66       Pancreas   0.71Fat        1.06       Fat        0.76Mammary    96.03      Testes     0.47Adrenals   42.43      Adrenals   40.87Ovaries    7.22       Prostate   3.54Bladder    7.77       Seminal    0.88Muscle     1.16       Bladder    3.80Skin       3.58       Skin       1.36Uterus     3.74______________________________________