Organic compounds -- part of the class 532-570 series – Organic compounds – Cyclopentanohydrophenanthrene ring system containing
Patent
1998-09-15
2000-11-14
Badio, Barbara
Organic compounds -- part of the class 532-570 series
Organic compounds
Cyclopentanohydrophenanthrene ring system containing
C07J 900
Patent
active
061472352
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for hydrogenating unsaturated plant-based compounds with a polymer-bound catalyst containing grafted groups. The invention further relates to regeneration of a catalyst. The term `unsaturated plant-based compounds` refers herein to non-hormonal unsaturated plant steroids and to unsaturated fatty acids and their triglycerides.
BACKGROUND OF THE INVENTION
Steroids are macromolecular, non-volatile and thermosensitive organic compounds with a complicated structure. They are used for many special purposes: as pharmaceuticals, additives in foodstuffs, cosmetic products, etc. They are often produced on a small scale, and the same multipurpose reactor is used in steroid syntheses for various reactions, such as hydrogenation, oxidation, reduction and esterification.
Steroids are a group of compounds with a similar structure. They are commonly present in plants and animals and include, for example, sterols, vitamin D, bile acids and sex hormones. The structure of steroids is based on the following 1,2-cyclopentenofenanthrene ring system: ##STR1##
Sterols are steroids whose structure contains an OH group. Sterols are crystalline C.sub.26 -C.sub.30 compounds, and they contain an aliphatic side chain at C.sub.17. Sterols occur in the nature either as free sterols or as esters of higher fatty acids. Sterols can be isolated from the non-saponifiable moiety of fats and oils. The best known animal sterol (zoosterol) is cholesterol. The best known plant sterols (phytosterols) are stigmasterol, sitosterol and ergosterol (yeast sterol). The structure of cholesterol is illustrated by the following formula: ##STR2##
The stereochemistry of the substituents at carbon atoms 3 and 10 is important for the hydrogenation of the .DELTA..sup.5 -double bond. If the hydroxyl group at C.sub.3 and the methyl group at C.sub.10 are both above the ring, they are at a cis-position in relation to each other. In steroids, a group of substituents above the ring is indicated with .beta., whereas a group of substituents below the ring is indicated with .alpha.. In all plant sterols, the hydroxyl and methyl group are at a .beta.-position.
The structure of sitosterol differs from that of cholesterol only in that in sitosterol there is an ethyl group attached to C.sub.24. The double bond of sitosterol and cholesterol is called a .DELTA..sup.5 -bond. Cholesterol is also known by the name of 5-cholesten-3.beta.-ol, and sitosterol by the name of 24.alpha.-ethyl-5-cholesten-3.beta.-ol.
Catalytic hydrogenation is a common intermediate step in steroid syntheses, for example. It is used for reducing various functional groups or for hydrogenating double bonds. Whether a hydrogenation is successful depends on whether the product is stereochemically correct. If the product is stereo-specifically incorrect, it is not suitable for further syntheses or for the actual application. The hydrogenation process of the invention is used for preparing steroids in which the H-atom at C.sub.5 is at an .alpha.-position.
According to the prior art, steroids have been hydrogenated by means of nickel black, Raney nickel, and nickel catalysts attached to inorganic supports. The activity of nickel metal has, however, not been sufficient for hydrogenating steroid double bonds. Steroids have also been hydrogenated with noble metal catalysts, particularly Pd- and Pt-catalysts. Hydrogenations have been carried out by the use of metal blacks, or noble metal catalysts bound to inorganic supports or to activated carbon. The best conversions of the starting material have been achieved with noble metal catalysts bound to activated carbon, particularly with the Pd/C-catalyst. It is generally known that the problems with the use of such a catalyst have been the separation of particulate catalyst powder from the reaction mixture after hydrogenation, the inflammability of the catalyst, and the fact that the catalyst is not recyclable.
Until the 1960's, the catalyst most commonly used for hydrogenating the .DELTA..sup.5 -double bond
REFERENCES:
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patent: 4427591 (1984-01-01), Ayer et al.
patent: 5326825 (1994-07-01), Nasman et al.
patent: 5412127 (1995-05-01), Mentink et al.
E.N. Frankel et al., "Hydrogenation of methyl Sorbate and Soybean Esters with Polymer-bound Metal Catalysts", pp. 349-354, American Oil Chemists Society Campaign, IL, Journal vol. 57, No. 10, 1980.
B. Gordon III et al., "Rhodium(I) Catalyst Supported on Polymer Crystal Surfaces: Further Hydrogenation Studies", pp. 2139-2142, Journal of Polymer Science: part A: Polymer Chemistry, vol. 25, 1987.
Hautala Matti
Helminen Jarkko
Hotanen Ulf
Karki Ari
Paatero Erkki
Badio Barbara
UPM-Kymmene Oyj
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