Duphar International Research Bv

Robert B Koolstra

Sebastianus J Halkes

Eric Goethals

Wolter Ten Hoeve

Hans Wynberg

Louis F Pauli

Alphons Dufourny

The invention relates to a method for the photochemical isomerization of organic compounds, in particular 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 a solution of the organic compound to be converted in the presence of a non-polymeric photosensitizer to light with approx. 300-1,000 nm wavelength, and by then isolating the resulting product, wherein a substituted thiophene derivative having a substantial absorption in said wavelength region is used as the photosensitizer. The invention also relates to a new photosensitizer to be used for said isomerization reaction.

Method for the photochemical isomerization of organic compounds under

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.

Method for the photochemical conversion of tachysterol compounds into

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Weesp, Netherlands

Robert B Koolstra