Patents by Inventor Robert B. Koolstra

Robert B. Koolstra has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Method for the photochemical isomerization of organic compounds under the influence of a photosensitizer
    Patent number: 5252191
    Abstract: 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.
    Type: Grant
    Filed: April 24, 1991
    Date of Patent: October 12, 1993
    Assignee: Duphar International Research B.V.
    Inventors: Louis F. Pauli, Alphons Dufourny, Robert B. Koolstra, Hans Wynberg, Wolter Ten Hoeve
  • Method for the photochemical conversion of tachysterol compounds into previtamin D compounds and of trans-vitamin D compounds into cis-vitamin D compounds using a polymeric photoinitiator
    Patent number: 5175217
    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.
    Type: Grant
    Filed: August 23, 1990
    Date of Patent: December 29, 1992
    Assignee: Duphar International Research B.V.
    Inventors: Eric Goethals, Sebastianus J. Halkes, Robert B. Koolstra
  • Method for the photochemical conversion of tachysterol compounds into previtamin D compounds and of trans-vitamin D compounds into cis-vitamin D compounds
    Patent number: 5035783
    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.
    Type: Grant
    Filed: December 7, 1989
    Date of Patent: July 30, 1991
    Assignee: Duphar International Research B.V.
    Inventors: Eric Goethals, Sebastianus J. Halkes, Robert B. Koolstra