Synthesis and spectral properties of estrogen- and androgen-BODIPY conjugates

- BODIPY and aza-BODIPY are attached to substituted estradiol, testosterone and 19-nortestoterone.
- Pd-catalyzed Sonogashira and Cu(I)-catalyzed click reactions are used to prepare the conjugates.
- Spectral properties suggest their potential as multimodality PET and fluorescence imaging agents.

To develop receptor based fluorescence ligands for imaging breast and prostate cancer, a series of estrogen-, testosterone- and 19-nortestosterone conjugates linked to BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) or aza-BODIPY, were prepared. Their synthesis involves attachment of iodo derivatives of differently substituted BODIPY and aza-BODIPY analogs to the C17α-position of the steroid moieties using either the Sonogashira coupling or Click reaction. The UV-Vis absorption spectra of the conjugates range from 500 to 710 nm with fluorescence emission properties ranging from 520 to 700 nm, facilitating observations in living cells and tissues. Selection of the site of substitution, as well as the type of substituents on the steroidal moiety and the use of different linkers, provides a library of fluorescing conjugates to explore the effect of structural modifications on biological properties.

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