Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1989-12-07
1991-07-30
Niebling, John F.
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
B01J 1908
Patent
active
050357832
ABSTRACT:
The invention relates to a method for the photochemical conversion of tachysterol compounds into previtamin D compounds and of trans-vitamin D compounds into cis-vitamin D compounds under the influence of radiation, by exposing the tachysterol compound and trans-vitamin D compound, respectively, dissolved in a suitable solvent system, in the presence of a polymeric photosensitizer consisting of a polymer chain ("backbone") comprising covalently bound sensitizers suitable for the photochemical conversion, to light with a wavelength of preferably between approx. 300 and approx. 1,000 nm, and by then isolating the resulting previtamin D compound and cis-vitamin D compound, respectively, in which a polymeric photosensitizer is used, the polymer chain of which has been selected from the group consisting of a polyether chain, an amino groups-containing polymer chain and a block copolymer chain comprising polyether segments and/or amino groups-containing polymer segments, in such a manner that the polymeric photosensitizer dissolves in the solvent system during the exposure to radiation but either upon cooling precipitates from the solution and can be separated, or, in case said polymer chain comprises amino groups, can be protonated with a suitable acid substance and be removed in an after-treatment. The invention also relates to a polymeric photosensitizer to be used for the said method.
REFERENCES:
patent: 4517125 (1985-05-01), Takayama
patent: 4551214 (1985-11-01), Hansen
patent: 4609444 (1986-09-01), Guillet
patent: 4686023 (1987-08-01), Stevens
patent: 4849076 (1989-07-01), Neckeys
Goethals Eric
Halkes Sebastianus J.
Koolstra Robert B.
Duphar International Research B.V.
Hsing Ben C.
Niebling John F.
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