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Studies towards the synthesis of photosensitizers with improved biodistribution and light-absorbing properties Johnson, Claire
Abstract
The objective of this work was to develop methods for preparing novel photosensitizer drugs with a) improved selective accumulation in diseased tissue and b) increased wavelengths of activation. The approach taken to enhance selectivity involved exploiting the upregulation of steroid receptors within tumorous cells. Porphyrinic photosensitizers were conjugated to a variety of steroids, ranging from cholesterol to the estrogens and androgens. A number of linking methods were employed: cholesterol was attached at the 3-position via a carbamate group or a diene tether. However, these linkages were non-ideal, as the products lacked the desired stability or existed as geometric isomers, and so improved techniques were sought. This led to the development of a palladium-catalyzed cross-coupling technique to link 10- iodo-5,15-diphenylporphyrin with hormonal steroids ethynyl-substituted at the 17-position. Using this method, a series of steroid-porphyrin conjugates was prepared. In an extension of this work, selective couplings were performed on 5-bromo-15-iodo-10,20-diphenylporphyrin, in which the iodo-group alone reacted under mild conditions. A second coupling under more rigorous conditions resulted in reaction at the bromo-substituent, creating a bifunctionalized porphyrin product. This provides an alternative method to the synthesis of asymmetrically-substituted porphyrins. Efforts at increasing the absorption wavelength of the photosensitizer lead to the design and synthesis of new chlorin systems based on octaethylporphyrin and possessing exocyclic nitrogen-containing rings. Through these studies three new types of chlorin chromophore were prepared, each absorbing above 670 nm. In addition, an unusual dimeric chlorin was unexpectedly formed, for which an X-ray crystal structure was determined. Finally, attempts were made to prepare analogous chlorins based on other porphyrin systems. As initial efforts at synthesizing a tailor-made base porphyrin system were unsuccessful, 5,15-diphenylporphyrin was chosen as the starting material. Studies aimed improving the synthesis of this compound were partially successful. A series of meso-substituted diphenylporphyrin derivatives was prepared in a manner similar to that used for the octaethylporphyrin analogues. However, these derivatives did not give rise to chlorin products.
Item Metadata
Title |
Studies towards the synthesis of photosensitizers with improved biodistribution and light-absorbing properties
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1997
|
Description |
The objective of this work was to develop methods for preparing novel photosensitizer
drugs with a) improved selective accumulation in diseased tissue and b) increased
wavelengths of activation.
The approach taken to enhance selectivity involved exploiting the upregulation of
steroid receptors within tumorous cells. Porphyrinic photosensitizers were conjugated to a
variety of steroids, ranging from cholesterol to the estrogens and androgens. A number of
linking methods were employed: cholesterol was attached at the 3-position via a carbamate
group or a diene tether. However, these linkages were non-ideal, as the products lacked the
desired stability or existed as geometric isomers, and so improved techniques were sought.
This led to the development of a palladium-catalyzed cross-coupling technique to link 10-
iodo-5,15-diphenylporphyrin with hormonal steroids ethynyl-substituted at the 17-position.
Using this method, a series of steroid-porphyrin conjugates was prepared. In an extension of
this work, selective couplings were performed on 5-bromo-15-iodo-10,20-diphenylporphyrin,
in which the iodo-group alone reacted under mild conditions. A second coupling
under more rigorous conditions resulted in reaction at the bromo-substituent, creating a
bifunctionalized porphyrin product. This provides an alternative method to the synthesis of
asymmetrically-substituted porphyrins.
Efforts at increasing the absorption wavelength of the photosensitizer lead to the design
and synthesis of new chlorin systems based on octaethylporphyrin and possessing exocyclic
nitrogen-containing rings. Through these studies three new types of chlorin chromophore
were prepared, each absorbing above 670 nm. In addition, an unusual dimeric chlorin was
unexpectedly formed, for which an X-ray crystal structure was determined.
Finally, attempts were made to prepare analogous chlorins based on other porphyrin
systems. As initial efforts at synthesizing a tailor-made base porphyrin system were
unsuccessful, 5,15-diphenylporphyrin was chosen as the starting material. Studies aimed
improving the synthesis of this compound were partially successful. A series of meso-substituted
diphenylporphyrin derivatives was prepared in a manner similar to that used for
the octaethylporphyrin analogues. However, these derivatives did not give rise to chlorin
products.
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Extent |
10376109 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-03
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061595
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1997-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.