DD237067A3 - METHOD FOR THE PRODUCTION OF MULTIPLY SPECIFICALLY TRITIUM MARKED CHOLESTEROL - Google Patents

Abstract

The invention serves to produce tritium-labeled cholesterol which is increasingly used in medical institutions as a tracer for pharmacological examinations, preferably of lipid metabolism, obesity and associated cardiovascular diseases. The aim of the invention is to provide a method which provides multiple specific labeled cholesterol in a simple synthesis. According to the invention, the object is achieved by dehalogenating 2-brominated 6b-bromo-cholestenones, which are readily accessible steroid ketones, which are stable and storable in crystalline form at room temperature, in solvents in the presence of Pd / CaCO3 with T2, either triply or in the presence of T2 double-labeled cholest-4-en-3-one according to the method of Collins and Hobbs (Aust. J. Chem. 18 (1965) 1049) via the appropriately labeled 6b-bromo-cholest-4-en-3-one in either triplicate or double labeled cholesterol is delivered.

Description

Field of application of the invention

The invention serves to produce tritium-labeled cholesterol which is increasingly used in medical institutions as a tracer for pharmacological examinations, preferably lipid metabolism, obesity and related cardiovascular diseases.

Characteristic of the known technical solutions

There have hitherto been described two methods for producing tritium-labeled cholesterol, which relate exclusively to the labeling in ring A.

1. Deconjugation of cholesta-1,4-dien-3-one (1) to cholesta-1,5-dien-3-one (2) and its reductone with NaBH ₄ . (Kaneko, C. et al .: Tetrahedron Letters 1973,2339). Subsequent catalytic hydrogenation of the resulting cholesta-1,5-diene-3β-ol (3) with T ₂ using tristriphenylphosphonium rhodium chloride gives / 1 a. ^2a-3 H / cholesterol (4) (Laumas, K., M.Gut. J. Org. Chem 27 [1962] 314).

2. Selective catalytic hydrogenation of cholesta-1,4-dien-3-one (1) with T ₂ to / 1 a, 2a - ³ H / cholest-4-ép-З-оp (5) (Evans, EA: " Tritium and its compounds ", London, Butterworths, 1974, p. 384 ff.) And its implementation via the corresponding 3-acetoxycholesta-3,5-diene (6) (Inhoffen, HH: Ber. 69 [1936] 2141) and NaBH ₄ reduction (Dauben, WG, JFEastham: J. Am. Chem. Soc. 73 [1951] 4463) to / 1 a, 2a - ³ H / cholesterol (4).

The methods mentioned have advantages and disadvantages. Thus cholesta-1,4-dien-3-one (1) must already be synthesized from cholesterol via 6 stages. The deconjugation (1) - »(2) leads to large yield losses because of the extremely high instability of (2), which requires the use of absolutely water- and oxygen-free solvents.

In the synthetic sequence (D- * (5) - * (6) - »(4), a specifically labeled cholestenone must be converted to enol acetate (6) in a strongly acidic medium (AcCl + Ac ₂ O) lost semistable position 2.

Object of the invention

The aim of the invention is to provide a method which provides multiple specific labeled cholesterol in a simple synthesis.

Explanation of the essence of the invention

The invention is based on the object. To specifically introduce tritium into ring-Α and ring-B positions of a storable steroid, and to convert the tritiated steroid thus rapidly and specifically into tritium-labeled cholesterol specific to ring A and ring B.

According to the invention, this object is achieved in that 2-brominated 6ß-bromocholestenones (7), which are easily accessible and in crystalline form at room temperature as stable and storable recognized steroid ketones are reductively dehalogenated in solvent in the presence of Pd / СаСОз with T ₂ , and either cholest-4-ene-3-one (7 a) or double (7 b) labeled according to the method of Collins and Hobbs (Aust. J. Chem. 18 [1965] 1049) via the appropriately labeled 6β- Bromocholest-4-en-3-one is converted into either triple (9a) or double (9b) labeled cholesterol.

a R ¹ = R ² = Br b R ¹ = Br; R ² = H

a R ¹ = R ² = T

R ² = H

a R ¹ = R ² = T b R ¹ = T; R ² = H

The use of (7 a) or (7 b) after catalytic reductive dehalogenation affords specifically highly labeled cholest-4-еп-З-on (8a and 8b), respectively, in the chosen fast, mild and one-pot reaction via the corresponding 6ß-bromoketone can be surprisingly converted to also highly specific labeled cholesterol. On the other hand, when unbrominated 6β-bromo-cholest-4-en-3-one is detected, only weakly labeled cholest-4-en-3-one and, correspondingly, weakly labeled cholesterol are obtained. The procedure conducted as a one-pot reaction also has the advantage that in addition to the 6ß-bromoketone and the excess NBs is reduced. Aprotic solvents, in particular benzene, have proven to be particularly suitable solvents. But it may also be mixtures of aprotic solvents ^ nsbesondere be used with ethanol _(.

embodiments

1. Synthesis of / 2,2,6- ³ H / Cholesterol (9a)

2,2,6β-Tribromo-cholest-4-en-3-one (7a) (12.4 mg = 20%) was combined with 5% Pd / CaCO3 (65 mg) and benzene (anhydrous, 3 ml) on a tritium gas labeling apparatus (Fig. hydrogen-free, 7OkPa) and hydrogenated at room temperature with vigorous stirring. After 60 min, the reaction was stopped, the remaining tritium reabsorbed, the catalyst filtered off and the filter washed with benzene. The combined filtrates were freeze-dried. After thin-layer chromatography with benzene / ether (19: 1), 2,2,6β- ³ H / cholest-4-εp-З-о p (8a) (5.46 mg = 71%) with A ₈ = 62.5 Ci / mmol (= 2300GBq / mmol) in> 99% radiochemical purity, 5mg thereof were refluxed together with N-bromosuccinimide (NBS, 13mg) in tetrachloromethane (anhydrous, 4ml) for 1h. The batch was filtered, the filter washed with benzene and the combined filtrates freeze-dried. The residue was taken up with bis- / 2,2'-dimethoxyethyl ether (diglyme, anhydrous, 2 ml) and treated with a suspension of NaBH ₄ (9 mg) in diglyme (2 ml) dropwise with stirring. After quantitative reaction (about 1 h) and thin layer chromatographic purification with benzene / acetone (9: 1), 2,2,6- ³ H / cholesterol (9a) (1,25 mg = 16%) with A ₅ = 73Ci / mmol (= 2700GBq / mmol) in> 99% radiochemical purity.

2. Synthesis of / 2, 6- ³ H / Cholesterol (9 b)

2a, 6β-Dibrocholest-4-en-3-one (7b) (20pmol) was also dehalogenated as described above. After work-up and thin-layer chromatographic purification, / 2a, 6β- ³ H / cholest-4-en-3-one (8b) with A ₈ = 21.8 Ci / mmol (= 805 GBq / mmol) was obtained in> 99% radiochemical purity. Meanwhile analogous reaction to progress the example to give / 2a, 6- ³ H / cholesterol (9b) A ₈ = 20,1Ci / mmol (= 745GBq / mmol) in radiochemical purity> 99%. The yield of (15b) was 20%.

Claims (1)

Invention claim: A process for the preparation of poly tritium-labeled cholesterol of the formulas 9a and 9b by reductive dehalogenation of bromine derivatives with tritium gas in the presence of Pd / CaCGv catalyst in a solvent, characterized in that first corresponding 2,2,6ß-Tribromcholest-4en-3-one or 2a, 6ß-Dibromcholest-4-еп-З-оp of the formulas 7 a and 7 btritiiert and tritium-labeled cholest-4-еп-З-on derivatives of the formulas 8a or 8 b obtained then in a known manner with N-bromosuccinimide and NaBH _{4 are converted} into diglyme.